It depends on the fanbase and how dedicated they are to it as well as the content it produces. But any fanbase can be toxic on both ends of the spectrum.I’ve noticed this too. I’m not part of many other diehard fan communities like the theme park community. Are other types of fan bases also typically this toxic?
I've witnessed the purity police go after small otherwise harmless because they didn't like one thing about something somebody else created. I've had friends get told to kill themselves over fanfic.
I typically do my best to avoid fandom. It's so much less of a headache.