Yea, agreed.
Brain-dump warning - armchair psychology and dumb analogies ahoy:
Our intention isn't to imply that being gay or bi or trans is wrong. I don't think people who use the term are necessarily implying that they are, either - many now identify as gay or bi or even trans themselves - that isn't to say it's not a slur rooted in some pretty messed up ideas, but it probably goes to show that for many, the fetish itself is about the perceived "wrongness", whether they personally feel it's "wrong" or not. A lot of kink is like that - social taboos and sexual fetishes being what they are. And going further than that, for some, it's a bridge to "wrongness", a way to make it feel alright. That's why erotica that features dubious or even a lack of consent is consumed by people who self-insert into the passive character: without agency, actual desires can remain subconscious and still be fantasized about, rather than envisioning themselves as an active, consensual participant who has to explicitly say, for instance, "do me up the bum!"
That might seem like a form of self-harm, but fantasies can remain fantasies, and for those who break themselves free of that kind of self-denying or even self-loathing thinking, it can still be comforting to fantasize in that same vein while consciously acknowledging that you're not being "trapped" or that you're not "trapping" anyone; you're seduced or being seduced by someone, in the typical fantasy case, who has a penis, and who has a gender and sexual identity that you are completely comfortable with, just as you're comfortable with your own. The "naughtiness" or "trickery" of it, then, is the same "naughtiness" or "trickery" as "you've been a very bad boy, and I'm a sexy cop, so I'm going to sexily arrest you, with sex." "Oh no officer, not with your boobs all over my face!"
This isn't a blanket excuse of "it's just porn" - we try to think about how people can take attitudes away from it (just a quick rundown of things we would want to clarify - sex isn't sex without consent; both men and women, regardless of any context, never deserve to be raped; men and women, regardless of genitalia, are people first and foremost and should be treated and respected as such; your gender and sexuality are just fine; gender isn't defined by noodly bits or what you wear for fun times; don't reduce whole people to fetish objects or objects of worship - it's still dehumanizing; be good to each other) We try to make it as explicit as possible when we're delving into themes for the sake of making a point about real life and when we are solely for the purposes of a fantasy, and it's always an ongoing process. Sometimes the best we can do is a disclaimer warning along the lines of "don't try this at home!", but it is notoriously difficult to avoid reinforcing some awful idea or another, even in something that seems otherwise innocuous. We're making smut that we hope to be inclusive with, not because we want to save the world through the power of dicks, but because it sucks to feel excluded or demonized for no reason, whether it's smut or not.
tl;dr - It's a slur; fetishes do as fetishes does; just because I think wearing lacy underwear is "dirty" and "naughty" in a sexual context doesn't mean I can't take pride in and enjoy wearing ladies unmentionables; dehumanization sucks.