He's clearly being blackballed and rightfully so. What rich, white business owner would want to be seen as aligning their franchise to this person who took some very public, very bold anti-American stances? The NFL knows who pays their bills, and it is some of the most patriotic, blue collar folks out there. It is well within the owners rights not to sign him so long as their isn't a league level collusion. I doubt there is.
No further discussion needed. He made his bed, now he's gotta lay in it. No denying he has talent, but he did something dumb and will pay for it.