From my perspective, the concept of the morality of coercion is a contradiction in terms. That is, I see morality at it’s most basic levels as being about making choices that respect the choices of others (at least coming from a perspective of self-ownership and property rights). Coercion, however, is the forcible removal of the choices of others. That said, the concept of govern, at it’s core, is an ammoral concept. The purpose of government is about the establishment of order. The interesting conflict between these concepts arises because, while we as a society have some basic morals upon which we can mostly agree, we also observe that the choices of everyone in a society of sufficient size cannot have sufficiently similar morals, or at least cannot be expected to actually be moral, and thus we must come up with some set of unified rules, and these rules must be enforced coercively. So what we’re left with is a balance between two orthogonal concepts of morality vs. order.
Now, I would tend to agree with the spectrum proposed by the OP that, in theory, if we had a population where everyone more or less agreed on what is right and wrong and everyone more or less could be trusted to follow it, then we’d need very little coercion from an authority to maintain order. On the other hand, considering that coercion is inherently immoral, it would seem to me that a given authority should try to appropriately balance the level of coercion with the level of order necessary for the appropriate society. If you have too much coercion, you may have order, but you also have an oppressive regime, but if you have too little, you may be allowing greater freedom, but you also have more chaos.
Further, like any multiple point optimization, I doubt there’s any sort of objective ideal point, so not only will that point vary from society to society just due to the inherent differences in those populations, but even in a given society, there will be disagreement about where that point is and how to achieve it.
But this is why, despite that I see morality as an essential part of the human condition and a consideration for governing, it is precisely that it is orthogonal to the concept of order that the idea of legislating morality is a bad idea. That is, sure, we can almost universally agree that murder, theft, assault, rape, etc. are things that need to be elminated to maintain order, there are plenty of things that we simply cannot agree on are necessary for establishing order or a universally agreed upon moral state, so it makes no sense to legislate that. So, for instance, while I have no desire to smoke pot or hire a prostitute, as common points of argument for legistlating morality, I also don’t see how it benefits society in a way that is sufficient to warrant that added level of coercion necessary to do so and, as such, in a sort of logical irony, I see those sorts of laws as immoral. Similarly, anti-homosexual laws ultimately result in reduced freedom and increased coercion, which makes those sorts of laws immoral for the same reason.