The pap was doing the old Ray Winstone "I'm from Laaaaandaaaarn, I'll have YA!!!" routine. It wouldn't happen anywhere else. He was looking for a reaction and successfully provoked one. No doubt if Bieber touched him, he would have sued for emotional distress, or some other similar bollocks.
The only blame Bieber gets is rising to the bait.
There was a lot more than just the "Pap" incident. He went out shopping in a gas mask. Late to two shows , one in Nottingham and one in London . Getting kicked out of a night club because he tried to get a 14 year old kid in.
ETA - Also kicked out of the Langham hotel and needing to move to 45 Park lane last Wednesday !