Generally, and in this case, I agree with that principle.
I don’t care how bad of an actor he was.
To an extent this is not as easily dismissible. A known bad actor has the possibility of being personally known to, and identifiable by one or more individual cops on the scene. This can legitimately go to probable cause for more scrutiny. It's a fact of life, but as I said, I don't have the information here.
While I agree that being a known “bad actor” could explain the police treating this particular person more harshly than might appear warranted, I don’t think that could ever justify shooting him while he’s down and doesn’t justify smacking him around while he’s not immediately threatening them. I have a lot of respect for the job police officers do and the stress they go through and understand that hindsight it 20/20 but given the power that we give police officers, we also have an interest in making sure that the people who don’t have the temperment for it aren’t given that power and to make sure that those who go way too far don’t literally get away with murder.