You can't have a character go 'BISEXUALITY ISN'T A THING' and then not address it at all, especially if the character whose sexuality-questioning inspired that comment eventually concludes that he isn't bisexual after all. Really, now.

Ugh. Having a character go "Bisexuality isn't real!" and having them shown to be wrong can work if done right, but when a show looks like they're confirming that idea, it's not good.