We're essentially talking about the categorization of some fetish mangos, this conversation has fuck-all to do with social justice or political correctness.
Come to think of it, that might actually be one of the reasons why most of the proposed splits would bother me.
"Gender-bender" (as used) is broad enough a term that it has some application outside of fetish tagging (e.g. it also includes manga that are playing with the idea of gender for literary reasons). Indeed, none of the current tags are specifically for searching for fetishes,
per se (the handful of existing gender-related ones come close, but that's pretty much unavoidable).
Honestly, being on a site where a lot of the genre tags were about fetishes would leave me feeling a little grungy. I get why they'd be important for the hentai side of the site (which you may be able to infer, I'm not really using), but... Oh, and having the tags makes it a topic of conversation in the comments, too, so it's a bit more complicated to resolve than just averting one's eye from the genre bar.
I realize that such complaints may seem bizarre, or an overreaction, to people coming down more on the "Internet is for Porn" side of the equation. We could talk at length about the illogicality of residual puritan societal values vs. the real or imagined dangers of sexual objectification—but my point was more just to explain how I feel about the matter.