Who's preventing him from working? Football requires reliability and because it's so public, a certain standard of behavior. If you're going to hang out with thugs and murderers and risk behavior that will get you suspended and unavailable to play, then yes, you risk getting cut. It's not hard to understand. Nobody has a right to play football in the NFL. Cutting him from the team for conduct is not preventing him from earning a living. That's a stupid argument.
Not only did he get in a fight, he rode in a vehicle where there's no way he didn't know someone fired shots from a vehicle in someone's direction. He kept quiet about it. Whether he knew someone was murdered or not, those are facts. You don't fire a gun at someone without some kind of intent.
So he was cognizant of that at the minimum and it can get worse from there. He's not some innocent bystander. He made his bed. He DID commit a crime by failing to report a crime. Playing football as a career is not a right. Get that argument out of there.