Obviously you don't understand the importance of the moment and black people. It not just a 'few' tribal cop. It's a hole community effected by injustice. I'm pretty sure if you had a higher chance of being killed, hurt, stopped by a cop because of you're appearance, you would want to do something about it. To many times I see people who don't experience inequality ( like women, members of the LGBT community, Muslims, and Darker skin people ) wanting to belittle the issues and experiences of less fortunate communities.
Also, it's not good to judge a whole group by the actions of a few. [ EDIT ] Not all members of the black live matter protest would advocate what went down in that video.