you don't know s***

You know what's annoying?
When someone contradicts you with a lot of conviction, so you don't argue because you assume they know what they're talking about... and it turns out they don't and you were right.

imaginary ex:
-This goes up I think I've seen it before and it was up, so I can assume this one should too no?
-No, no, this goes down!
-err... you sure 'bout that?
-yes yes, down!

turn the thing upside down, all its insides fall out and break

-well... erm... maybe they've changed it... it used to be down... yes... they fucked it all up!
-huh huh...
*leaves the scene thinking either I have no credibility or men are over assured idiots*