@Spyrits mob mindset and bullying the weakest were always a thing. What happened here was already foreshadowed in the first chapters when Yuri snapped and told a bunch of guys that the rumors were true and that there was a boy from the school who bought her, there's also the scene where mom almost snapped at Souta in chapter 4, so to call it forced is overkilling it. There were signs that shit was gonna go south for the MC since the beginning, also that school as a whole is a hivemind that orbits around the school idol, so if somebody does something offensive to her, he's doomed. It's not about him "buying prostitutes" or not. In the end, it's all about him being the ugly duckling of the school and not being like the other beta orbiters.
It ain't the same bragging about banging a whore with the people you trust and can keep a secret, with being socially killed by a scorned bitch that everyone in school beta orbits around her with baseless rumors even teachers don't buy it. And given Souta has no friends there, he, and us saw this coming.