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Would you not argue that it is self defeating to want stuff (things, possessions, and so on) but to simultaneously believe that it is wrong to steal? After all, a prohibition on theft makes it harder to amass things.

If you do believe these are contradictory, then I would say that it does not follow from the fact that these two forces act against each other, that they are morally incomparable. Sure, one makes the other harder, but that obstacle is justified by the moral stakes (namely that taking things that could have reasonably been acquired otherwise is harmful). And as a consequence, your argument is invalid.

If you believe that a prohibition on theft and amassing wealth are morally compatible, I would ask why you think these two opposite forces are compatible, but taxation and amassing wealth are not.

Still don't understand how theft could NOT be considered wrong, but maybe I miss something. I will just copy paste my answer to another comment below, maybe that will clarify my position:

"The taxation was perceived as "punitive": because they have so much, they should intrinsically and unquestionably suport a different level of taxation. The focus of the questions is on the cognitive bias which creates a conflict between wanting to have a money but stopping any action towards this goal because you hold this belief that having too much money should be taxable punitively. That sends the message that too much money is bad, somehow.

At least that's my understanding of it."

You can't understand because it's absurd. The question is: why don't you think it's similarly absurd to oppose taxation on the grounds that it makes amassing wealth difficult?

The "punitive" thread is a red herring. The wealthy are not taxed more aggressively MERELY as punishment, anymore so that theft is prohibited MERELY to be punitive. The punitive impulse is in response to an already established prohibition. In the case of theft, it's a prohibition against taking what isn't yours, and in the case of taxation, it's a prohibition on hording resources to the harm of others.