I fully agree that a lot of cops are too trigger happy, too taser-happy also. I've been utterly disgusted by video of cops beating the shit out of an already helpless and subdued suspect, especially when there are like 6 cops on him. The worst I saw was Robert Leone I think was his name, white guy... look up the long vid on YouTube about it, totally disgusting.
Police brutality and excessive force are real problems. Police also sometimes go too far with racial profiling or treating minorities worse (though I think a lot of this is due to who is committing what type of crimes and I think there is a valid role for a certain degree of racial profiling)
I also agree that this particular case is a little bit in the grey area, but when I look at all the facts here, and look at the video, and think about it... I don't believe it is appropriate for this officer to face any punishment for what he did here.