>>531631435
Both teams spent time in each other's universes and saw how the general public treats superheroes. Both teams concluded that the other were inherently evil because of the world's they come from: Justice League think the Avengers are evil because Marvel Earth is a shithole, so therefore they must be corrupt assholes. And the Avengers think the JLA are evil because they're treated as actually beloved heroes, so therefore they must rule as tryants forcing everyone to love them like living gods. As far as "dumb reasons for the good guys to fight each other", they could've certainly done worse