Giving up your back = rolling over to avoid being punched in the nose = dumb, but nevertheless pros do it plenty.
I doubt green was trained above watching a UFC or two. His mount looked incredibly unbalanced and unpracticed, sitting that high up.. if you cannot escape that mount you have a serious problem and should stick with something more like embroidery. Absolutely powerless as well. Coulda gone on for hours, no ko potential, and could dry hump him hugging his neck indefinitely. Both are jackasses, clearly fighting for nothing other than to show off in front of a group/camera.
Knowing anything about fighting is a mixed blessing, the confidence and idea that it could save you were you/loved ones to be hurt is nice, but most people that are gona mug you are probably going to be armed (I always picture that scene in Indiana Jones and The temple of Doom? with the sword master that Indy just shoots after he does his little sword tricks). I've only been involved in one streetfight (pointless) and looking back on it now, I would have rather lost. The legal system is half retarded, the winner of the fight has a very difficult time proving both parties are equally responsible.
This weeks fight on the ultimate fighter was a much better example of a "vicious beat down". Bisbing made Kristian look like had absolutely 0 business being in the cage. Painful to watch.