> It's actually quite rare to find someone who says I will help the poor, but only if my neighbour also pays, otherwise they can get fucked

You are seeing all of this in a very, very black and white way. It's about how much the average person is willing (or forced to) to contribute in either system especially when you try to scale it up to hundreds of thousands or millions of people. Libertarianism is an utopian ideology not particularly different to Communism in the sense that both are incompatible with human nature.

I mean there is simply no empirical evidence this approach scales beyond small high trust (usually homogeneous) communities. Tragedy of the commons is a thing.

> your sadistic MAD view where you punish the poor

That's extremely reductive... and you are making this way too personal than it should be ; )