I hasten to add that I only view it that way because the art is good – indeed, as you point out, it’s superior to legitimate public art. A lousy artist wouldn’t have the same moral license to get away with this sort of thing.

Does that imply an ethical dualism where some have moral rights (although not legal rights) that others don’t have? Yes. On the margins of the law, in the spaces where you can accomplish major good with minor infractions, the competent have more moral license than the incompetent.