We as a society give police officers power, and expect in return to have that power used appropriately, and within reason. Sometimes that stretches as far having to subdue through force, punching, or even killing if necessary. Those that hold that power need to be held accountable if they abuse their position, though I firmly support the right of the officer to do whats nessesary to protect himself, or any other bystanders. Unfortunately in this case we don't know what happened before the excessive force occurred, but it was pretty clear to me at least one blow was completely unnecessary. Thats one too many.
I couldn't be a cop cause if someone spit on me or attacked me, I don't know if I could stop myself from going overboard. Thats the job, an officer of law should be more professional than you or I, and should be held to a higher degree of accountability. As should all of our county, state, and federal workers, from comptrollers to senators, when fuckery is detected, it needs removed. If a police officer can't control his temper, he shouldn't be a police officer. Just my .02.