I wouldn't have cheered the Durant injury if I was in the crowd and this was a Celtics game, but I think the situation is being overblown. This is a fanbase that has been passionate for a while, and until this season were universally mocked for being a regular season team that always got steamrolled by the "real" contenders, and have suddenly found themselves a game away from beating one of the greatest dynasties in the history of the sport. When Durant went down, they had a sudden reaction that they suddenly had a much greater chance of winning the championship; and they cheered that. They shouldn't have, but I don't think it's an incredible indictment of the entire fanbase, and people panning he entire Raptors franchise and fanbase, and apparently the Toronto metro area in general, need to reel in their hot takez a bit. When Durant was walking off the court, the fans apparently gave him a standing ovation a "KD, KD, KD!" chant.
Also, especially for the fans in the arena, it wasn't immediately clear that Durant had seriously injured his achilles, for all those immediate reactors knew, he had just re-aggravated his calf again and needed to put some ice on it. A lot of this after-the-fact hand-wringing is indicating that Toronto fans cheered that Durant tore his achillies, but that isn't really telling the whole story since those people had no idea at the time how severe his injury was.