I'd just like to ask the people considering the PCs violent thugs to, when they visualise the PCs, include tanks, close air support, ICBMs, a large chemical arsenal, powered armor, and the like to their visualization. Again, PCs past a certain level aren't criminals, they're four-man rogue states. They simply aren't problems that can be solved by hitting them with a hammer, because they can move faster than your hammer and can retaliate with larger and larger acts of brutish thuggery.
In real life if a cop is rude to me I can't just kill him even if I am say head of one of the most powerful crime families or head of a powerful church. If I do there will be consquences. It is just stupid.
Say you're the head of a crime family with your own personal army, which is at least within an order of magnitude of the army of the state you're in. There will be consequenecs, yes, but they will involve things like strongly-worded letters of protest (or alternately, quiet assassination and/or massive first strike scenarios), as opposed to "You're just a punk."
It's hard to visualize this manner of thinking, especially for those of us who grew up in the U.S., where the government will win against pretty much any private agency. I think, for optimal visualization results, these expectations should be used. Say that a group of foreign military agents (in plain-clothes, making it ambiguous whether or not this was black-bag or simply recreational) killed a high-ranking CIA agent in a domestic dispute. Say that said foreign nation had a significant army, a reputation for utter ruthlessness, first-strike capacity, and a stated intention to treat unjustified assaults on its citizens as an act of war. Do you think that the first result of the U.S. government would be to start off by trying to shoot or arrest said agents? I think that, provided additional threat/provocation isn't offered by the agents, we'd start off by trying to find out, in detail, what the hell happened, and would avoid solutions that lead to war.