"Douche" is a method of contraception. I'm pretty sure (s)he isn't a method of contraception. Please use suitable words that fit the context.
To "douche" is to use water or a mild saline solution to flush the mucous membranes from the walls of the vagina. It is no longer medically recommended to do outside of specific scenarios/conditions, as it removes the bacteria and lymphocytes that act to prevent various infections.
The slang term became used as a way of referring to someone who thinks he/she is cool, but is really not. A 'douche' thinks he is cool because he has something to do with vaginas - but he's just cleaning them out, so it's not as though he's a god of the bed.
Catching on?
Anyway... a lot of me thinks Hiashi is/was of the type that tries to 'motivate' people by berating and insulting them. It would work for characters like Neji - who are head-strong and would be motivated by an insult to his abilities - and possibly for Hanabi. His words were meant to, in a way, piss Hinata off and get her to prove him wrong (and, possibly, to get under the skin of Kurenai and motivate her to train Hinata in a way that would prove him wrong, too).
I think it's pretty clear that it didn't have the desired effect. It's just not Hinata's personality.