All human societies are self-organizing. How could they be otherwise? Who is organizing a society other than the people in it? God? Hardly. Even colonialism and imperialism are self-organizing: once the people in one country, culture or society start interacting with people of another, they create a new society composed of both the original societies; the organization is coming from within that larger society.
All human societies are "democratic" in a sense: the self-organization comes from the interaction between all the people. Even the most brutal, tyrannical slave society is the result of the interaction of all the people in that society, including the slaves. If all things considered the slaves preferred rebellion to slavery, they would rebel; that they do not shows that all things considered they prefer slavery. And even in a the purest direct democracy, there will be great differences between the power of individuals to affect the course of society. There are individual differences in intelligence, discipline, focus and will, and there will be organizations or ad hoc collections of people that differ in the overall focus and unity.
I'm not trying to justify slavery or any other objectionable political or economic system. I'm saying only that a "meta-analysis" of how a society is organized is not a useful way of distinguishing between societies. You can't abstract away the details; you have to look at the specifics of how a particular society has organized itself to make any kind of judgment about that society. It's absurd to say that thus-and-such society is bad because its social organization was "imposed from without"; there is no "without" from which to impose a social organization.
It often appears that some social organization is imposed from within by a minority. The United States Constitution and much of its legal and political doctrine was created not just by the capitalists, but by an elite within that class. (And there was immediately a factional struggle within the capitalist ruling class between the federalists and the anti-federalists.) But it's important to understand that the capitalist class was able to shape society precisely because the combination of individual and aggregate qualities of the capitalists combined to give them power disproportionate to their raw numbers. Furthermore, their individual and aggregate qualities, as well as the power of the group, were all shaped by global properties, by their interaction with everyone.
This principle can be succinctly summarized as, "The people know what they want, and they deserve to get it good and hard."
All societies conform themselves to their present-day economic necessities. Economic necessity exerts as profound a selection pressure on social evolution as it does on biological evolution. Elements of social organization that lead to sufficiently poor economic performance get selected against; what remains in a society is sufficiently well-suited to economic necessity to not be selected against. But, just as in biological selection, economic necessity does not entail or force an optimal system or any specific social system; it merely eliminates certain kinds of egregious sub-optimality.
A lot of social selection happens inside our heads, which means that social evolution can occur much faster than biological evolution. We can consider social elements abstractly in our thoughts, and eliminate elements we consider sub-optimal or otherwise objectionable, without actually trying them in physical reality and letting them succeed or fail. We can also transmit ("inherit") and consider social elements (ideas) individually, which means we can try many more different combinations of elements than we can in biological evolution, where an organism is stuck with a random collection of heritable elements from its parents, and all biological selection can operate on is the organism as a whole*. (To a certain extent, there are biochemical selection pressures that operate directly on the heritability of individual genes, but phenotypical selection can operate only on the organism as a whole.)
There's an interesting theoretical consequence of the above view. There will always be variation within the ideas of a population. Since human beings are genetically homogeneous and more or less socially homogeneous, people will sort themselves out into groups. The interactions of all the variations mean that the members of some groups, by virtue of their individual characteristics and the aggregate characteristics of the group, will have more power proportionate to their numbers to fulfill their immediate desires. Other groups, for the same reason, will have less power.
This is a scientific truth. This truth, however, leads to the naturalistic fallacy: Because some group actually has power, it therefore objectively "deserves" power. It is therefore "wrong" for another group to take power from the first, regardless of the changing mix of individual and aggregate characteristics and the conformance of that mix to changing material economic reality.
It is not the case that communists are (or should be) against capitalism because the capitalist class does not "deserve" power. (The construction "does not deserve" is ambiguous: it can mean there is such a thing as objectively deserving, and capitalists lack that property; it can also mean that there is no such thing as objectively deserving, and it is a category error to speak of this property as if it did exist.)
It's rather that communists are (or should be) against capitalism because they observe the disconnection and contradiction between modern economic reality and the traits and characteristics of the capitalist ruling class. By introducing new traits and characteristics into the population, and by creating their own group with its own individual, aggregate and global characteristics, we can introduce a new set of social constructions to the evolutionary mix, social constructions that better meet more needs, economic, political, social and psychological, of many more people.