Though he’s correct about the gene not being identified yet (nor is there one for straight people), there does seem to be a little bit of science indicating genetic and biological factors in determining your sexual orientation. Like, I dunno, lesbians and straight men have the same size brain hemispheres, as so do straight women and gay menmore likely you’ll be gayhave longer ring fingersstartle response differencesto be left handed more oftenbetter memories than straight menhair generally rotates differently (seriously); and many, many more!
All of this is irrelevant to the fact his argument has no bearing on a person’s right to equality. Share so he knows you care.