Well as a cyclist I would like to come to that cops defense.... CM has been going on for quite some time, its a good idea 'in theory', but then theory and reality are often worlds apart.
In the video we (or any one else I imagine) could not see what the rider may have done off camera. We dont have any idea why the cop reacted in that way (or what some other rider that may have come along before the tackling dummy) Critical Mess has become quite 'confrontational'.
The idea behind it is to only 'inconvenience' drivers to make them aware of bike riders. Not beat them up or insult them or for that matter break the law. In the last 5 years there has been more and more violence having to do with Critical Mess, riders attacking car drivers, car drivers running down riders.
Because of its very nature (no organization, no leaders) there is no way to insure that participants behave in a sensible fashion, no one to take the blame when things do go wrong. That and its been growing and growing.. its dangerous by very nature (disrupting the flow of traffic, you mix motored vehicles and bikes with no rules, no wonder more people have not been hurt.....)
Well speaking as a cyclist... I think its a bad idea. You see breaking laws is not really that good of an idea to start with, but then to go and rub it in someones face.... Ya Im running these red lights, and theres nothing you can do about it... well its a bad idea. They are not promoting cycling only provoking motorist. Encouraging more bad blood. You see motorist already perceive us as an annoyance, so going and making them angry by blocking up roads once a month, then insulting any poor motorist that happens to get stuck in the mess. Sure that guys gonna LOVE cyclist. The confrontational nature of it just goes against the intended goal (MHO) that and I AM a cyclist, I AM on the road every day (Unlike many of the goofballs that you see sy CM who come out once a month to *beep* people off, get something pierced or tattooed and then go back to their apartment, cave or huble to drink and torture small farm animals or what ever it is 20 somethings do now in off hours..

) so I do care what motorist think.
The sign says SHARE THE ROAD, that means cyclist too.
Just one example of things getting out of hand, over the last 5 years or so I have noticed that there are more and more of these every year. Last year it was an elderly couple in SF, had their wind shield broken out, and tires flattened.
http://www.thenewstribune.com/news/promos/wirepicks/story/424949.html