Did you see all of the video? If someone is stopped by the police they need to do what the cop tells him/her to do. If the person resists detainment/arrest, repeatedly disobeys instructions, keeps reaching for something(which could be a gun) and/or takes a swing at or kicks a cop, he’s going to be roughed up. It sounds like the perp was on drugs, kicking and fighting after multiple tases.
“Did you see all of the video? If someone is stopped by the police they need to do what the cop tells him/her to do. ”
He was NOT the person “stopped by the police.”
So you have no argument, by your own words.