Talking to Entertainment Weekly, actor Andrew Garfield was quoted saying he'd asked his director "What if MJ is a dude?' Why can't we discover that Peter is exploring his sexuality? It's hardly even groundbreaking! … So why can't he be gay? Why can't he be into boys?"
Somehow that translated to someone asking Stan Lee at Fandomfest in Louisville, Kentucky, if Spider-Man could be bisexual. Here's Stan's response.
"Who says.. he's becoming bisexual? Spider-Man? Who have you been talking to? I don't know, seriously, I don't know anything about that. And if it's true, I'm going to make a couple of phone calls. I figure one sex is enough for anybody."