I still don't think the officer singled out that specific cyclist. The two officers were looking up the road at a large group of cyclists. I think they decided it would be best to get out of the way and started moving towards the sidewalk. The bad apple COP let one cyclist go by and then decided to walk forward.
He and the next cyclist got confused and ended up colliding. I agree that his big step forward and shove was uncalled for and certainly makes him the aggressor. I just don't see any evidence that his action was directed at that specific cyclist as some are claiming.
Also keep in mind that these Crit Mass events often put the police it a bad spot. The cyclists are forming a demonstration without a permit (I think). They are breaking traffic laws. The motorists are looking at the cops saying, "WTF, Why don't you do something about this?" Tensions are high and clashes often occur. This one is pretty minor, IMO.
To me it looked like what he did was pretty blatant and pre-meditated, but I do see Ben's point. If you're willing to give him the benefit of the doubt, there were several bikes wizzing by him at a pretty good speed swerving by him before and as he was making his walk to the sidewalk. It is possible he saw one of them as trying to hit him. If you are standing in the middle of the road with 1000's of bikes going by you, it is possible you see something of an illusion.
Again, my opinion is it was much more premeditated than that, but that's how I would defend the cop if I had to.