As to ancaps being selfish; I can certainly appreciate where that idea comes from.
We believe that debts can only be accrued deliberately.
If we agree that I take your car today and pay you $10,000 a week from now, that's a legitimate debt.
If you imagine that I owe a percentage of my income to support the poor, but I haven't agreed to that, I'm going to make a point of
avoiding paying; and you're going to consider me selfish.
If I claimed that others should be taxed, but not me; that would be selfish.
Ironically, many taxation cheerleaders get more in welfare than they pay in tax; making them selfish by that definition.