*If the state doesn't promote the good and inhibit the bad, it is faulty; if there is no sense of good and bad (moral nihilism, distinct from subjectivism), then the state is nothing more than the coercive arm of the ruling class, but so what?
Consider murder, defined here as one individual killing another "on his own nickel, i.e. without an explicit social process. There is the value of not getting killed*, and the value of killing people one individually chooses. There is the labor necessary to support police, courts and prisons, and the individual labor necessary to protect oneself against people who would kill him. An economist is going to look at where all the marginal values and costs intersect, at both the personal and social level: Our spending on police and prisons should be where the marginal utility of having one more person murdered is exactly equal to the marginal cost of preventing one more person killed.
*High, but not infinite, as demonstrated by the many people who have consciously placed themselves in circumstances where they had a significant probability of getting killed. Besides, come what may, we're all going to die someday.
It's also the case that coercive force, whether exercised by individuals, the state, or some other institutional arrangement, exerts selection pressure on the the "meme pool", the ideas, beliefs and habits of thought in the population. The selection pressure can be direct: killing or imprisoning a person can eliminate or reduce the propensity for his ideas to spread*. The pressure can also be indirect, because people can anticipate consequences: some will simply believe that crime doesn't pay.
*One argument against the modern prison system, however, is that "criminal" ideas are more heritable in prison.
At first glance, therefore, it would seem that we want to make our law enforcement costs about equal to the average cost of crime. However, this effort has differential selection. There is a range of intelligence, cunning, and will among individuals, and law enforcement will differentially select those nearer the bottom of that scale: cops catch stupid crooks. Thus law enforcement and criminality starts off an evolutionary "arms race", a phenomenon seen both in biological evolution as well as business. Indeed the business "arms race", where individual firms compete (in the ideal case) to provide greater value at lower cost, is one of the strongest arguments for capitalism*.
*Not strong enough, of course, to justify capitalism.
The ideas of ethics, politics and economics are so deeply interconnected that they really are the same thing, viewed from different angles.