Wait, is this really the reason?
I've easily seen way more than a dozen people literally use the term "hate" or "despise" to describe how they feel about him, some have claimed he's a horrible human being and plenty didn't hold back in saying how they reveled in watching him have a seizure after getting blasted by Emmett... which is fucking sick.
The reasons you gave give good reason to have a chuckle about him believing stupid stuff like flat earth but for people to be straight up losing their shit because he thinks that stuff is real gives off serious psychological red flags about them and not Bryce. Is it political? If so, that just makes it worse and displays how consumed they are by that stuff.
Are you sure he didn't do something horrible to another person or has a criminal record or something that actually would qualify him as a bad person where the hate might be justified?