First, the guy was there drinking long enough to get completely hammered and pissed off. That means there was about a 99% chance everyone knew he was a cop by the time this started.
Second, the beating he was handing out wasn't anything nearly life threatening.
In a case like this I'd do what someone else apparently did. Call 911 and report a beating in a bar and then, probably, try to de-escalate the thing when he comes up for air. If Rico was there and tried to tackle that cop, a few things would happen:
1 - He'd get his ass handed to him in a way he can't even imagine. If he started to get the upper hand, the off duty would pull is backup and kill him.
2 - If he survived the fight, he'd end up in prison. While in prison, the corrections officers would ensure he got paired up with Hugo the giant p3nised sodomite every other day. Because he is there for assualting an officer. AIDs is inevitable once Rico starts being passed around in exchange for cigarettes.
3 - Rico dies in either case, saving the world from any further burden of carrying his defective genes.
The End