> From where do you derive the need to protect people from the total consequences of their failure or misfortune by forcing the collective to bear the burden?
I'll answer this with a question: you said elsewhere that its unethical to compel doctors to treat a patient. Let's assume that's the case. What happens when you are robbed by someone, shot, and your wallet is stolen, you even pass out from the shock and blood loss.
A bystander calls an ambulance. Then what? The ambulance service, the hospital (and the doctor) have no idea if you can pay for their services. Let's assume you can, you have fantastic insurance. What is the right way to resolve this situation? It seems to me your answer is that the hospital should have every right to refuse to serve people without identification (and in fact this is probably in the hospitals best interest, from a pure ROI perspective).
So do we throw our hands in the air and let some people who, by any account, don't deserve to die (they're insured, if their wallet wasn't stolen, there'd be no issue at all!) through no fault of their own, or do we protect people from the total consequence of their misfortune by providing some kind of guardrail?
A more general answer is that people, in aggregate, don't like the instability that comes from a lack of welfare state. If you provide absolutely no welfare state, and I lose my job and can't find a new one, it is very likely that the best thing for me to do is to steal from someone. And people generally speaking dislike that because unlike robbery from the government, which involves paperwork and court rooms, that kind of robbery really actually involves guns. And people seem to find suits and paperwork to be less force than guns.
So you pick your poison: a democratically controlled nonviolent robbery that you can influence and plan for, or a stochastic violent robbery that you can't control at all. Personally, I find paperwork to be less violent than a gun, but you have weird ideas about what constitutes violence, so I'm curious what you'll say.
> What's the problem with strictly voluntary, at-will, consensual interaction between people?
It doesn't exist. Is coercion voluntary? If it's violent to threaten someone's life by holding a gun to their head, why isn't it violent to withholding food they need to live (or the money they need to buy the food they need to live, or the healthcare they need to live, or the money they need for that healthcare)?