I'm gonna be real with you OP, I don't think cops should handcuff and throw down with someone for a missing registration. I don't see how this situation would arise at all if cops de-escalated properly, as they're all supposed to do but none of them seem to know how.
I'm sure this guy was acting like a clown, but there should not be an obvious straight line from missing registration to resisting arrest, and I'd be surprised if the cops didn't provoke this in some ways.