Good one! Hang on... you aren't being serious are you?
It's a hell of a trick to have a standing leg "taken out" but then not fall over until a split second after! Let's put it this way. If Bale had won a penalty by diving like that (which actually he hasn't), I would not be on the Gunners board defending him!
He was joking. Even Wenger wasn't blind enough to pretend they weren't lucky to get it.

Where have I justified it? My point is if you go around being a provocative winner against your bitter rivals, you're going to get hit with something.