> I'm aware libertarians believe it's the principle of the thing, dammit, but I'm truly weary of arguments which boil down to "Elizabeth Warren's wealth tax is philosophically indistinguishable from a call for nationalizing all industry."
First, while some wealthy people remain wealthy, I'd guess there's a much larger impact on people who are becoming wealthy than those who are already super-rich.
Second, as you said, it's the principle. I've got an objection to seizing people's stuff to then give away to others. There is no reason government should supply anything that is not a pure public good, and it should supply precious few of those, too. Remember that every act the federal government takes is backed up with the threat of death. If you don't comply, a bunch of agents will bust down your door at 3 AM and haul you away (see the disturbing number of paramilitary groups many federal agencies now possess). If you resist, you get killed.
This applies to income tax too, by the way. I couldn't care less how much good you think you can do with it, no one gets to take someone else's stuff because he wants to give it to someone he deems more deserving.