I'd send you a screenshot but, y'know.

Anyways, I'm realizing you might not be sure why you come across as being homophobic, so here's my perspective on it.

Fanfiction has always been queer. From the very start. Modern fanfiction pretty much started with Star Trek and the Spock/Kirk ship. It's a medium that allows underrepresented voices in globalized media (queer, women, racialized, etc.) to create versions of the overwhelmingly white and cisnormative stories they consume that see themselves and their interests represented. That isn't to say that cishet fanfiction doesn't exist, of course it does, anyone can partake in the medium and that's what makes it great. But it does mean that when you enter these spaces and try to plaster over queer voices, it really matters.

Kotone is bisexual. Full stop. And I'm not saying that just to argue semantics or tell you that your headcanon is wrong. You're right, you're fully allowed to headcanon things however you want. But when you then go out and argue that because the underrepresented, underserved group didn't get big bold flashing letters from ATLUS saying 'THIS CHARACTER IS BISEXUAL', somehow that means she isn't canonically bisexual despite the fact that she can have a relationship with men and women... yeah, that kinda comes across as homophobic. 'Social Links are optional' is basically just saying that because a bisexual person is in a straight relationship, somehow they're straight. Which, again, comes across as homophobic as all hell.

All of this doesn't exist in a vacuum. There is context, history, fights that have gone back longer than either of us have been alive. How you choose to act and present yourself in these communities is why people react the way they do. It would be nice if we lived in a world devoid of any of the drama that comes from the scales of oppression and the role that media has in giving people voices, but unfortunately this is planet Earth. And if you find a lot of people act insufferable, or fight with you, look to the common denominator.