And somehow Trump is really popular and 'out-spoken', 'honest' and 'direct'.

Well, calling her a bitch is an insult directly associated with the fact that she's female. If you found a gender-neutral insult that means the same thing, then by all means, call her that.

It's not the act of insulting that is the problem in a lot of these cases. It's the specific insults used that cross into less PC territory.