Exactly, one can speculate, but to defend a bogus speculation is even more retarded.
As far as the cop. It's fact that the cyclist was the suspect of a criminal complaint ealier for violating traffic laws and weaving in and out of cars. He was endangering drivers by his actions. The cop obviously recieved his orders to detain this cyclist. It was not because the cop didn't like the guys bike, and decided to take him out.
No, he was accused of doing so by the arresting officer, they guy who attacked him. I lost count at 30 bikes in the video, and at the time the cyclist is attacked there is another cyclist in the shot also wearing a white tee shirt and black shorts. Exactly how was this allegedly wanted cyclist identified among not less than (and many more than) 30 cyclists as the wanted man?