That doesn't rule out him being bisexual. He can date Mary Jane after he dates Human Torch. It causes a stir because the Fantastic Four didn't want him on their team, probably because they have a good image and he's a menace. But Johnny doesn't care, because he's a bad boy, and flaming to boot. This, of course, will piss all of the ladies vying for Peter's attentions as of Endgame, resulting in the most convoluted and sexy love dodecahedron in history. Make mine, Marvel.