* People should keep their money, they worked hard for it!
Then Bruenig points out that there is capital income, which does not come from work. Capital will keep "working" for you even if you stole it or inherited. It's extra obvious in the case of owning fully autonomous robots that could do anything a human could, but it's true for much simpler forms of capital, too.
Then they retreat to voluntarism:
* OK, so capital owners didn't work to get that money, but it was all voluntary. I'm just against force and for voluntarism.
Then he points out that property rights are enforced through violence too - the only reason you will make those "voluntary" trades for food and shelter, is that men with guns will come and arrest you if you just take it.
Then libertarians retreat to common-goodism:
* OK, we could imagine a society where people could just take as they please, so property rights are in a sense man-made. And they do require violence to enforce. But not having them would lead to the tragedy of the commons. Without property rights, we would all be miserably poor!
And this is certainly true, but if the common good is what we target, why not have a proper welfare state, a solid UBI funded by high taxes etc.?
Usually at that point they go back to the first step.