Diogenes didn't exactly tell him to fuck off, it was more that he made a request for him to move over as if Alexander was literally any other man on Earth. An equal. Which arguably is more insulting as I'm sure Alexander's enemies often told him to fuck off, but this was the first time he was requested to stand aside by a dude known to publically masturbate.

Later, Alexander found Diogenes picking at the bones of a long dead servant, and when Alexander inquired as to what Diogenes was doing, Diogenes replied that he was trying find the difference between these bones and the bones of Alexander's father. Zero fucks given because in the end we are all bones.