That is true. However beating to death a now secured perp is a different matter entirely. When that is tolerated and accepted then the practice gradually spreads to anyone these cops feel deserves it. And that is a very slippery and dangerous slope. A lot of so called law abiding liberals think this would be perfectly acceptable treatment of a peaceful TEA Party demonstrator. Do you really want to head in that direction?
If you continue to resist, you need to be subdued. If you are in compliance, then no, they should stop the use of force. The problem many times is they are trying to subdue drunks and drug addicts who do not even know where they are. Know someone who was beaten up pretty bad by Long Beach Police over 10 years ago. He was drunk and being a menace. When a short police officer walked into his cell, he stated, so you come to take my lucky charms ? That was why he was beat up and he later realized he kinda deserved it. Police are humans after all.