You don't get a 20k fine for a bit of banter. The AFL investigated and know what was actually said.
I guess it's like Melbourne not tanking, and essendon not taking drugs. We all know what was actually said, but the AFL will let the masses argue Rather than actually making comment
It's not what was said, it's the timing. I've said this all along. What is there to be gained at the end of the game to gloat and taunt? The game is over. There's a reason he was fined was because of this.