I don't see why or how. They liked the character as he was before the age up. Making Jon swing both ways doesn't change anything about. Just because a character shares the same sexuality as them doesn't make real difference as to their existing problem. People aren't like light switches. A minor change that doesn't fix the existing major problem you have with the character or even doubles down it isn't going to get the result you. I think it's kind of insulting to think that Bi or Gay people who didn't like the age up are suddenly going to support it just because Teen Jon, who they didn't want, is kissing a boy. You're assuming that the only thing LGBT fans care about is see LGBT sex/romance and that overrides anything else they may be interested in.