I'm not sure if all refs are like this, but something I dislike about EPL refs is their habit to watch incidents at HT and do the best they could to even things up if they've seen a mistake. Following the interval there were a few incidents. Arteta gets thumbed in the eye and goes down, free kick went WBA's way for obstruction. Mertesacker got booked for his reaction after he made an excellent tackle that the referee called a foul on. Cazorla bought down hard outside the box directly in front of the ref, no free kick.
Happens in every game, referee will give decisions out of nothing to balance things up a bit after viewing replays at half time. This is neither fair nor right. They should not watch decisions and they should rather call everything down the middle, no bias.
In yesterday's game West Brom didn't really take advantage of the ref's second half leniency and instead argued with the linesman over spoilt milk. Guess the ref had enough of being lenient at that point and gave us a second penalty.