Why does everybody suddenly hate the Celtics?
1. Lakers fanbase is probably the biggest in the NBA, and the two teams are rivals
2. In the East:
A. the Knicks have a classic rivalry, more of general NYC and Boston thing
B. Nets fans tend to dislike Celtics fans for gloating over picks. Also the Kidd Nets vs the Pierce Celtics, especially around the 2002 ECF.
C. Pistons fans, mainly going back to Bad Boys and Bird days
D. Hawks fans, mainly going back to the Dominique-Bird battles. Celtics were major stumbling block
E. Sixers fans, probably 2nd most "even" alongside Pistons, although Pistons fans don't seem to care as much past the origin of the rivalry. You have Wilt vs Russel, young Bird vs veteran Doctor J, etc.
F. Cavs fans, going back to Lebron's struggles against big 3 Celtics and then vice-versa
G. Heat. Part of this is Lebron and Big 3 vs last of Big 3 Celtics, along with Ray Allen joining the Heat. Part of this is Pat Riley, who went from Showtime Lakers to a tenure with the Knicks (although the Celtics were trash at that point) to the Heat.
The Heat and Pistons part are probably less relevant today due to a cool-off, and I don't think there are any Nets fans on here, iirc.
More relevant, is that this year's Celtics team somehow gets into drama with every single team they play in the Eastern Conference. They have things with the Raptors, Knicks, Hawks, Knicks, Cavs, but the most heated one is probably with the Wizards. It's not that they're dirty or anything, some teams or players just do that, and it could easily be a thing they do the motivate themselves. In any case, it's fun to see.
The Lakers are sort of similar in the Western Conference with how many "rivalries" they have, with almost every team claiming something against them. For the most part, the only teams with legit two-sided rivalries with them in the Western Conference are the Spurs, the 2000s Blazers, the 2000s Kings, the Suns, aaaand that's probably it. Pistons and Celtics and maybe Sixers(?) from the eastern conference.
Only difference is that the Lakers are trash atm, so no one cares too much about them