I wasn't coming up with ways. Those are established facts and established rules in the NFL. If they want to, they can do it. He signed the contract.
They seldom renege on bonus money because players are suspended. They have the right to but it's not an everyday practice.
They would probably prefer the league to handle this but what about conduct detrimental to the team? Is there anyone on that team proud to have Joseph on it? First, he doesn't do the right thing and then he's rat. There are some people that have more of a problem with the latter.
Then there is the lack of criminal charges just like with Watson. There's huge difference between what the two of them did but still if the law is not going to do anything but cut him a deal for ratting his friends out, what is the NFL going to do? And how would the NFLPA respond to action taken by the league office?
You've got almost half the voters in that thread that want him kept on the team. There's your societal view and the reason it is disintegrating.