I see you conveniently chose to ignore the part about that tweet that was actually important. I bolded it for you. There's nothing there about being teased or bullied, though...
After being informed that his teammate/friend was contemplating suicide, Incognito continued to relentlessly mock the guy and allowed others to do the same.
Again, I'm not against locker room culture and lowbrow humor, but there were red flags all over this situation. If anything, this quote completely destroys your position that nobody knew anything was wrong, and nobody could have been reasonably expected to know since he didn't tell them.
The fact that Incognito didn't take that conversation as a turning point, have his teammate's back, and try to actually help him, says a fair amount about the guy. I'd still take him on the Patriots, because he's really good at football and it seems that most of the locker room liked the guy and had his back. But it's clear that he's the kind of guy that needs to be policed and held in check. When you go in the polar opposite direction and allow someone like him to set the tone of the locker room... well, you get the 2013 Dolphins.
Side note: who doesn't have a friend like that? A well-intentioned guy who is also a socially ******ed and takes everything way, way too far, to the point that he alienates people for no good reason. I assume we all know someone like that, and the answer to how to deal with them is always the same: that person needs to be held in check by the rest of the group: you need to force him to dial it back when he's too dumb to realize he should be doing it himself.
Every social group that I've ever been a part of--childhood, high school, college, and post-college adult life--has contained at least one guy like this. He just doesn't know where the line is, and if he isn't held back by the rest of the group he'll go to really weird, really dark places in the name of 'just joking around'. It's pretty ****ed up in a lot of ways, but if you genuinely think that he's just trying to fit in and doesn't realize how much of an ******* he is, you tolerate it, and you handle him by holding him accountable, establishing boundaries, and calling him out when he crosses them.