Mineta is one of the most hated characters in My Hero Academia, not just by several of the characters on the show (especially the female ones) but also fans. He is lecherous, perverted, and a bit of a coward. A subset demographic of fans now hate him more because Mineta would be a crass representation of a bisexual. Mineta potentially being bisexual plays into the trope that bisexual people (particularly bisexual males) are promiscuous predators who are not to be trusted.
There is little solid evidence of Mineta being bisexual. Most of the speculation comes from the My Hero Academia manga Chapter #321, where Mineta says to Deku, "I fell for you." This is hardly a case for his sexuality. Still, more hinges on the fact that English translations are not always solid, whereas looking into a more accurate translation from Japanese has Mineta stating that he "admired" him. For those living in the West, the reaction to Mineta being perceived as bisexual may feel the same as what happened to the latest iteration of Superman coming out as bisexual. Jon Kent, son of Clark Kent, came out in Superman: Son of Kal-El #4.
This is not the fairest comparison of the two however since the Superman comics state Jon's sexuality outright, and he even has a boyfriend named Jay Nakamura. This relationship also seems positioned to present a much more positive representation of a bisexual male character. Needless to say, both caused an uproar in their respective fan communities for different reasons. Some fans of Superman viewed Jon Kent coming out as a cheap shot (even though it is not the same Superman but his son) at queerbaiting. Mineta being perceived as bisexual, on the other hand, brought some outrage because Mineta is a disliked character, and his sudden sexuality reveal (at least in the eyes of some fans) is shaky.
Does the whole Mineta debacle mean that My Hero Academia has no positive representation of LGBTQ characters?
The answer is a resounding no, and queer fans have to look no further than the character of Tiger, who was, in truth, the first confirmed LGBTQ character in My Hero Academia. Tiger, whose real name is Yawara Chotaro, is a trans man who is part of the hero team of the Wild Wild Pussycats. This character in the series might not have been told in explicit detail that he is a trans man. Still, according to My Hero Academia's manga author, Kohei Horikoshi, Tiger was a female assigned at birth who transitioned into a man in adulthood.
Some reading this may scratch their heads and ask why such a discussion matters, why is the sexuality of a character of great importance? For anime fans of the LGBTQ community, it matters a great deal. Seeing characters like them that can be heroic breaks away from the stigma of being queer and can teach kids growing up with an LGBTQ identity that they can be noble heroes and respected by their heterosexual allies without having to hide their identity. It also shows viewers that a queer person doesn't have to resort to being a caricature or a stereotype to be a queer representative. Another factor comes into play with characters, and that is romantic bonds. To have a queer character that is both of positive representation and being in a loving relationship would make many LGBTQ fans of My Hero Academia jump for joy.
So what does this mean for the future of LGBTQ characters in My Hero Academia? Maybe someday, fans of the show will see a pro hero akin to the wonderful non-binary superhero character, Fire Emblem, of the anime series--Tiger and Bunny. Only time will tell, but Tiger is a good start. My Hero Academia is no stranger to introducing characters who are multi-layered and fun to watch and considering Tiger, viewers might find themselves rooting for an LGTBQ main character soon.