I think some people think it's some kind of fetish that people have been conditioned into having. That's probably why it's so easy for them to lump it with the actual fetishes and call for an end to the whole lgbtq+. It doesn't help that people with fetishes now say they were "born that way". Like, yeah sure- you were born getting a sexual rise from wearing ski gloves, a toboggan hat, and a honking clown nose, somehow. I would care a lot less if people like that could admit it was something acquired during their lives and not tie it in with SSA.

And yeah, I encountered many different people who sounded like they didn't believe lesbians, gay males, and bisexuals exist at all.

To my first point, I should add that there are also people, who not only believe SSA doesn't exist, but believe LGB(especially LG) put active, sustained effort into refraining from opposite-sex relationships to pursue same-sex ones. Like it's some sort of rebellious act, meant to stymie "normal" people and undermine the concept of the nuclear family, the church, society or something else. Which can make them very indignant. It really is not seen as a real thing for these people. Subsequently, the term "Sexual Orientation" is completely redundant to them since they believe there is no other way people can be oriented.