So you're barely a grown up yourself, that's okay. But your view of what is mature and immature will most likely change a lot, the more you age, because you'll likely learn to better understand where the other is coming from.
I know there is a lot of negativity in the MMA fanbase in general, it really isn't about Izzy. And, in my experience, haters are far more toxic than fans, in general, but obviously a fan of one fighter could be the hater of another fighter. In other words, a person could be both a fan and a hater.
Making generalizing statements of fandoms isn't doing anything either, besides being negative yourself. It's not giving any of those haters/fans any reason to reflect on their own behavior, and if anything they just see your negativity as a reason to respond back with negativity.
Your perspective is probably also skewed a good bit, because the fans that are giving you shit you notice a whole lot more, than the fans who aren't giving you shit. But the ones who are giving you shit might very well be the vocal minority, which would make it unfair (or immature) to criticize the whole fandom.
Making a thread just to complain isn't really a very mature way to go about dealing with toxic fans, either. Like some have already suggested, it's much better to just ignore them, or actually own them in a debate with rational arguments, if you're equipped for that. But just complaining doesn't do a whole lot more than being negative without looking for a solution to your problem.
So in short, by complaining you risk getting caught up in the vicious cycle of MMA fandom's toxic behavior, that you're complaining about.
