because without fail it was always perfectly fine and justified and fair when they were doing it but nobody else should ever be allowed to for any reason
I think many are like this now in multiple domains. I reckon it has something to do with people being more self-centred, meaning that they only think about others, when they are affected negatively, but don't think about how they affect others.
That works too. I always figured it was some kind of cognitive dissonance, because I think most people would consider themselves "good" people, but affecting someone else negatively is "bad", but as they are very definitely good people there's no way they could be doing something bad therefore whatever it was they did can't be that bad or was justified or whatever therefore they didn't do something bad.