It's funny how libertarians think that once you remove government, all human interaction will be voluntary.

Humanity is barely keeping itself in check in a complex system that has developed over time, with multiple forms of organization, and multiple levels of checks and balances. Most attempts at massive restructuring has failed horribly, either if it's been in the direction of socialized organization, or private organization. Both were supposed to lead to flatter structures and less abuse, but in fact lead to the polar opposite.

But at the quip of an internet comment we're expected to realize in a flash of insight that "oh! it's so simple! if we just do it like this it will all be perfect."

In their defence, if we all really just did it like this, it really will all be perfect. Communism only failed because they didn't remove enough problems and over-extended their limited resources. Look at the Amish for a successful example.

I think you could pull off a Libertarian utopia with a very strong, very cruel dictator.

I will be sure to inform these private SWAT teams that I do not wish to engage business with them when they bust down my door.

Obviously, the fact that they consider themselves private is a farce. They're clearly a public entity.

You are not volunteering to engage, you are an externality in someone else's transaction. It's comparable in the outcome to your life. Though admittedly there is a difference in that the single entity purports to obey rules that they claim are for your good while the other multiple actors aren't likely to have expressed any concern for you at all.

You don't voluntarily engage with police or prisons whether they are government run or private corporations.

Are you suggesting that engaging with the market is purely voluntary? I'm not sure you can call something "voluntary" when not doing it inevitably results in destitution and homelessness.