what this sentence means?

[enyafriend]

Originally Posted by Hackimoto

We all know you know your Japanese, but why do you always have to be such a douchebag about it?

Rina said:

He's not really being a douchebag. Giving wrong information/information you're not sure about is no help to anyone. Better to keep your mouth shut and let someone who knows do the talking. The OP was asking for a fact, not opinion

Yeah, ditto.
Wise man says....do not try to act cocky and keep your mouth shut.