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It's the threat that's the problem. You walk into the bank and hand a note to the cashier, that's all you've done. If the note's a deposit slip, everything's good.
If the note's a threat and a demand, then we have a problem.
To say, They gave me the money so I didn't have to hurt anyone, while technically true, doesn't make the act any less a violent robbery.

All true.

I guess the other side to the discussion is that everyone benefits of varying degrees from shared infrastructure, but if some people refuse to pay their share, what's the fairest way to compel them? And do we as a society agree with those measures?

I don't think most people legitimately fear prison if they don't pay their taxes, but the fear of extra fines is definitely real and motivating.

I hear what you're saying... there's no real way to opt out, unless you move to a country with little or zero taxes... or you're rich and can pay people to find loopholes for you.

You could make the argument that it's necessary theft; but it is theft.
Kinda like cannibalism. Sure, your plane crashed in the mountains and you have no food, and Larry's dead anyway. You can argue that it's necessary cannibalism, or justified cannibalism, but it is cannibalism.

I'm just not sure what the alternative is though. We all need a certain level of shared infrastructure to survive, to be productive and to be happy. When people describe an area; they talk about safety, parks, transport, schools, etc - I'm just not sure how that happens without taxation.