Based on Edge's report my belief would be that prior to the election he was a relatively behaved individual who was more or less liked in the locker room despite relatively split political opinion differences, but that since the election he has constantly antagonized certain teammates about 1) the election results, and/or allegations of election fraud (this is a common theme I see among some of the out-there right wingers), 2) disparagement of BLM (this is another common theme among right wingers and would be backed up by the Heatley rumor of him yelling "Blue Lines Matter," at Kreider), and 3) other assorted political disagreements and/or personality conflict with Georgiev. The organization and the league know his history; his prior conflict just a week or so ago with Quinn reinforces his uncoachability, and then when he comes to blows with teammates for a dispute he is certainly at fault for (bringing antagonistic politics to work despite being told to knock it off), this seals the deal for him. As only 4 teams have cap room to claim him outright, in conjunction with his reputation being solidified as a problem personality, he will not be touched.
Based on the evidence we have available to us, that is my guess as to what happened.
I do not think there was any component of outright racism to this as that would have certainly alienated Miller from him but that doesn't seem to be the case.
Instead it's far more believable to me that he espoused views (for example, perhaps he called BLM a "terror organization," or something as I've heard conservatives do before) that are controversial and trigger some to levy accusations of racism where in fact it's really just political disagreement. I mean, a poster here a few minutes ago just said "Trumpism is racism," basically, so if that's your definition of racism then yes Tony is a racist and so are the 80-million or whatever who voted for him but I'm just not going to subscribe to that definition of racism, I would really need something way more overt than support of a political candidate over immigration policies or an opinion about marginalization of minorities by itself in order to conclude someone was a racist. Tony does have past history of slurs so there is that which is pretty overt, but that's not what happened here it seems, it seems like this was political aggravation.