The problem is that many of them have convinced themselves that heterosexuality is 100% biological, natural, and, therefore, "not a choice" (based on divine intelligent design).
They embrace the opposite view of such a binary: it apparently means, in their minds, that homosexuality (and anything else outside of heteronormative relations) is inherently "unnatural," not rooted in science or biology, and, therefore, "a choice." That's why they accuse us of wanting "special rights."
They use this belief as a pretense for trying to make same-sex marriage illegal again, while attempting to ban any discussion of homosexuality in schools.