The thing is Zombie, that her is the “nephew” of Celestia, so his family we know of or nothing like what he acts like, as for Trixie, we know nothing of her background, so we really can’t say why she acts that way.
Why is that Blueblood is a mostly an intolerable douchebag in fan works while Trixie gets a much more sympathetic portrayal?
He seems more clueless than antipathetic.