this
normies either won't know what undertale/anime/who your waifu/whatever fandom you're part of and if they do they'll think you're some socially inept neckbeard
a rule of thumb is to keep things from the internet out of real life
itt: don't identify with your interests because we don't like it
Having an avatar is nothing like wearing a tshirt. You aren't necessarily trying to pass off that your avatar is you, it's just that your avatar is the only visual representation of "you" when it comes to forum boards and the likes. This is why if I set my avatar to asriel from undertale, I would be associated with asriel and undertale every time I post
Normally this wouldn't be a problem if so many mongoloids didn't get bent out of shape when they see things they don't like.