Still no excuse for the officer to kick the guy in the head and try to get him again.
Worst of all is he's trying to spin it as an attempt to subdue him, despite the fact he's already on the floor, been tasered, and is being restrained by another officer.
Circumstances will almost certainly justify him getting angry and lashing out. He's just been punched multiple times, seen two female officers get laid out in front of him, it's understandable that he saw red and acted excessively but he's decided to go for a lie that he acted in a rational and considered manner.