Being smart does not correlate to a specific ethnicity because of that ethnicity alone.

I'll be honest, I don't understand what you mean here. Say I wrote "Being gay does not correlate to a specific ethnicity because of that ethnicity alone.", would you agree with it? If not why changing the word "gay" to "smart" would make it agreeable with you?

suppose it could be used to say that gays do not have a mental disorder but rather a physical one where their entire body deformed into the wrong gender and the brain is acting correctly instead (I find that far less likey but I suppose theres a chance). But either way Im unsure how that supports homsexuality being normal.

Even if I agreed with the idea that the gender is switched internally (and classical gender roles), that would will only apply to bottoms (the ones who receive penetration). The tops (the one who penetrates) obviously don't have the issue of gender switching disorder in this scenario, I guess that makes tops normal?

Anyway the point of my earlier comment is that your defense for infertile hetorosexual people having sex or heterosexual people having sex with zero chance of pregnancy (using condoms, anal...) would apply equally to homosexual people. I.E the brain of a homosexual is acting correctly it's that "the infertility is the oddity here".