If nobody wants to hire him, wouldn't that cause his market price to drop toward league minimum?
and he doesn't fit their offense;
I would not know about that, but even if he fit their defense like a non-OJ glove, his girlfriend comparing the team owner to a slaveholder definitely sunk his chances. It is generally not a good strategy to insult you prospective employer.
BTW, he's getting plenty of support from military and ex-military, who understand the actual rights they were fighting to defend.
Again, one of the isues is that he insists on protesting while on company times, wearing company uniform.
Content (anti-police, pro-#BLM) is an issue too, but content should and does not affect his right to protest. If he was protesting on his own time, there would likely be no problem.