The NFL is all about results. Winning and losing, making the playoffs, sell outs. You are calling GMs whose careers are on the line "cowards". You cite Jackie Robinson. Robinson was a Hall of Famer whose teams won 6 NL pennants and a World Series. Yeah, you shake it up for a talent like that. If you're not sure of the talent it's not difficult to understand the reluctance to make waves. Team chemistry is real and legitimate when your job is at stake.
So if i'm reading this right, the problem with MLB racists was the black players weren't out of the this world talented like Robinson, not that those players were powerless before the racist owners?
The NFL right now is way too permissive of bigotry and even overt threats and *that's* the problem.