Great discussion in this thread. Differing viewpoints but most of them expressed intelligently and respectfully.
I don't favor Shelton's dismissal (yet) though it wouldn't break my heart if he decided the grass was greener in, say, Oregon.
Still, this is not about the latest tweet but rather a pattern of behavior going back to last season. Any single incident is not a show-stopper. Put them all together -- it's a problem.
It seems like the time for an intervention has come...for the good of the team and the kid. And JF has exactly the combination of street cred, leverage, and communications skills to pull it off:
Antonio, we're aiming high next season, and we need your help to get there. That means no more locker-room distractions, dumb-ass tweets, racially divisive lectures, on-field misbehavior, and so forth. You have a bright future in front of you, young man. Don't (mess) it up.
Something along those lines, delivered in the appropriate tone with some colorful language -- and maybe a piece of broken furniture or two to emphasize the point.
After that, one more incident, and it's a lost cause. Those are not easy conversations to have, but when you're in a position of authority, which means coach...boss...parent...whatever...it's your job to have them.