- The police here were dealing with their adrenaline pumping.
Can I use that excuse if I beat someone up?
Well, you took what I said out of context. The context - everything that happened - is also important.
I said here that attacking him that way wouldn't be justifiable if he had just done something like loitering and refused to leave a place, or public intoxication, too.
Even for something more serious, if he peaceably surrendered from the get-go, that would be altogether different. In this case, he had been resisting arrest for a long time, and not just willfully and recklessly endangering the lives of police, but the public, too.
And given how little he showed respect for authorities and others, it's easy to think that his "surrender posture" might not be sincere, but some sort of trick. The choice to overwhelm him with physical force neutralized any possible future threat from him.