It has been alleged (and I use the passive voice on purpose) that communism entails a kind of "radical altruism," which is ineluctably contrary to human nature. In the most direct form, communism is criticized because it entails that every individual completely abandon his or her own well-being for the "good of society." I'm skeptical that very many canonical communist thinkers have actually made this case outside of a purely revolutionary context, e.g. "The fear of death is the beginning of slavery,"* but even if they did, the idea of absolute altruism can be discarded while still keeping the core elements of communism: worker ownership of the means of production and the ideal economic society of "from each according to his ability, to each according to his need." The best justification for communism is not altruism but utilitarianism: communism produces the society that creates the greatest good for the greatest number. Thus, a moral or psychological critique of communism entails showing either that communism cannot be reasonably expected to create the greatest good, or that utilitarianism (instead of radical altruism) is philosophically or psychologically untenable. The first critique is beyond the scope of this post; I want to focus on the philosophical and psychological status of utilitarianism.
The philosophical critique of utilitarianism falls into three categories*. First, utilitarianism requires a "felicific calculus," to use Bentham's phrase, which is overly simplistic or unnecessarily elaborate. This critique, while mostly accurate, does not address utilitarianism at a fundamental level. It's clearly possible to talk about utility in a consistent way: we can, for example, just ask people whether they are happy or unhappy. To say that it is difficult to measure utility does not say that we should not maximize utility if we could measure it perfectly, or maximize utility as best we can measure it. It might or might not be a valid critique that we cannot indirectly measure utility well enough to make utilitarianism useful, but it is simply invalid to say that because we cannot measure utility directly or perfectly that utilitarianism is fundamentally unsound.
*There are actually four, but the fourth consists of arguments based on one or more logical or rhetorical fallacies, such as defining utility narrowly or objectively (contradicting a fundamental premise of utilitarianism), arguing that utilitarianism is flawed just because it is different from something other than utilitarianism, or the ad hominem argument that utilitarianism fails because Bentham was an architect of capitalism and had some very stupid, horrible ideas.
The second critique is the "Omelas" critique: even if we could measure utility perfectly, there are (approximate) maxima of utility that profoundly violate our moral sensibilities. Ursula LeGuin's short story, "The Ones Who Walk Away from Omelas," is the canonical example. I have addressed this particular criticism earlier at greater length; one obvious counterargument is that we have no reason to believe — and many reasons to disbelieve — that there could possibly be any causal relationship between torturing a child and a happy society. It's possible that different laws of physics might render a society like Omelas meaningful, but our own moral intuitions, like our physical intuitions, were constructed by and are about this world.
Furthermore, utility is fundamentally subjective; a social structure that causes many people to have severe moral pain is by definition counter-utilitarian. If Omelas did not cause such severe moral pain, there would be none who walked away. Omelas therefore does not, even within the premises of utilitarianism, maximize utility.
The Omelas critique is fundamentally empirical, not logical. All variations of this argument make two premises. First, we have perfect information about what maximizes utility; second, based on that perfect information, the maximum of utility violates our moral intuitions. There are three counterarguments. First, we do not and cannot have perfect information; if things were different they would be different, and we are concerned with morality in this world, not some hypothetical possible world in which people have perfect information about utility. Second, there is no reason to believe that if we did have perfect information, the maximum of utility would actually violate our moral intuition; if such a case could could be proven in this actual world, we might reconsider utilitarianism, but, as best I can tell, such scenarios are entirely hypothetical, not real. Finally, even if we could determine conclusively that some maximum of utility actually did violate our moral intuition, perhaps it is our intuition that is defective, not utilitarianism. Again, we would have to thoroughly understand the trade-off between utility and our intuition in the real world to make a reasoned judgment.
The third critique is the psychological critique. According to utilitarianism, each individual should choose each of her individual actions based on what is best for all people, with her own personal utility a mostly insignificant residuum of that calculation. It seems readily apparent from introspection and common sense that not only do people not actually think this way, it is completely unreasonable to expect them to. A moral system has to be built on the psychology of people who live here now, and it would be presumptuous to discuss the morality of our descendants a thousand years hence, who might have a psychology compatible with our notions of utilitarianism. While utilitarianism does not demand that individuals completely ignore their own well-being, the diminution of their own utility to statistical insignificance comes pretty close. However, this is a fundamental misreading of Bentham's own work: although it is one legitimate way of understanding utilitarianism, it is not the only legitimate reading, and it is not how Bentham explicitly asks us to read the fundamental principle of utilitarianism.
Crucial to understanding utilitarianism is the fundamental impossibility of actually computing the greatest good for the greatest number. There are two problems with such a computation. First, it is computationally intractable. There are too many dimensions, one for each individual's desire; even if each individual had only 100 identifiable desires, we would have to solve 700 billion simultaneous equations to compute maximal utility. Furthermore, there are dynamic effects: changes in the world produce changes in our desires, in our subjective opinions about utility. Second, as noted above, we do not have very good measures of how our actions will affect other people's utility. Even if we could solve 700 billion simultaneous equations, we don't have the numbers to plug into the equations. If utilitarianism required that we perform a computationally intractable task without data, it would be an obvious failure. Fortunately, utilitarianism does not require such a task.
We cannot calculate for every decision which choice is best for everyone, but we can estimate which choices make the total utility better. We cannot maximize total utility, but we can increase total utility. And to do so, we need not, as individuals, ignore or minimize our own utility. We cannot consider our own individual utility to be a priori better than others', but each individual can consider himself an "expert" on what his own utility actually is. In the Introduction to A Manual of Political Economy, Bentham makes this point clear: "[W]ithout some special reason, the general rule is, that nothing ought to be done or attempted by government." Bentham argues that in the general case, total utility is best improved by each individual maximizing her own utility: "Generally speaking, there is no one who knows what is for your interest, so well as yourself—no one who is disposed with so much ardour and constancy to pursue it. . . . Each individual bestowing more time and attention upon the means of preserving and increasing his portion of wealth, than is or can be bestowed by government, is likely to take a more effectual course than what, in his instance and on his behalf, would be taken by government." Generally, Bentham asserts that we can just satisfy our own interests without worrying about computing the effects on total utility, and when we can make larger statistical calculations, those calculations are "special," not general. Bentham himself does not expect individuals to reduce their own interests to statistical insignificance, and indeed it is only in special cases that we need to consider statistical calculations at all.
Bentham is not contradicting himself. When I improve my own well-being without harming others, insofar as I can actually calculate, I am thereby increasing total utility. And, by and large, that is what civilized people actually do. If I want a hamburger, I just go get a hamburger. I am improving my own utility without, as best I can tell from our social agreements permitting the sale of hamburgers, harming others. And I do not harm others in satisfying my desire: if there is a line at Burger King, I don't bully my way to the front: it is unacceptable to improve my utility by getting my hamburger now by making others wait longer. I don't steal the hamburger; I work to earn the money and then pay for it. Some might assert that eating hamburgers in general harms total utility more than it satisfies our individuals' desire for hamburgers, but they have to prove "some special reason" why this is true, and in making their case, no individual's desires are a priori more important than any others. We have the goal of always improving total utility, and we move closer to that goal using the tools we actually have; there is no need to require tools we do not and (probably) cannot have.
A lot of people, myself included, think that this is precisely how a civilized, liberal society ought to work. Generally, we satisfy our own desires, not because our own desires are a priori more important than others, but because we are experts in our own desires, and generally, we can more effectively improve total utility by exercising our expertise than by any other means. We fulfill our own desires, as best we can tell, without harming others. When our desires come into fundamental conflict, we have to look to special reasons, which do not take any individual's or group's desires as a priori more important than any others. To the extent that we have "moral principles," we use these principles not as absolute truths, but empirical regularities that we believe improve total utility under conditions of uncertainty, risk, and hidden information, and we can change these principles when our understanding of reality, or reality itself, changes. Far from being psychologically radical, utilitarianism is completely ordinary social reasoning for many people.
Communism is in principle utilitarian. We may be mistaken, but communists believe that communism is the greatest good for the greatest number. We focus on workers because workers are the largest segment of society, because workers can improve both their own and others' utility without harming anyone, and because everyone can be a worker. The only utility communists seek to diminish is the utility of rentiers, and only to the extent that rentiers' utility is, by definition, gained at the diminution of workers' utility. I cannot think of a better utilitarian argument.