If anyone watched the US Indoor Champs this weekend (especially the men's 1500 meters), you would see that the so called "stiff arm" or "push" was nothing more than a sign of affection compared to what was going on at US Indoors.
Also, I don't see why anyone at all has brought up the fact that Leeder was completely impeding on Mulherin. Leeder had not established position at all after passing Mulherin. He began cutting in too early causing Mulherin to lose balance and put a hand on Leeder's back to maintain balance.
I don't care if Mulherin is a douche, he doesn't deserve to be disqualified.