The way I see it, that BMX rider simply shouldn't be in the road.
Given the nature of a BMX bike, he would get the jump after a stop at every light but would spin out early because of the low gearing. These means:
1:He gets ahead of everyone else at the beginning
2:Gets passed by everyone else almost immediately after/or holds up an entire line of faster cyclists due to dense traffic
Being a BMX bandit on a commuter lane just doesn't work well. If he can't handle being mechanically limited by his bike, he needs to deal with getting passed and not being a violent sociopath. Even if he did pass successfully he had to pump pretty hard. I can't imagine him pumping the whole ride just to stay ahead of the camera cyclist, who would have inevitably caught up and passed him again anyways.