I've never thought Rodney was intentionally being an ass, it's just he had no patience for stupid people, which in most cases was anyone else in the room.

They would rightly assume he's being an ass, he'd think they're stupid and not bother to correct them. Nice defensive mechanism to not deal with people too. It wasn't until people actually started listening to him and actually caring about what he thought about about him that he finally started opening up.

But then I'm biased. ;)