Support. Look up "intersex". It's Biology.
Before we understood them better, our society called them hermaphrodites. With further advancement in the science of Biology, our society has more evidence that those with XXY chromosomes exist. There are limitless variations of this type of deviation from the "norm" (for lack of a better word). That is why we say "assigned at birth" for those that want to transition. Because in a less tolerant and more ignorant world, the parents could choose what sex the child was assigned. And a lot of those times very inhumane and barbaric surgeries were done on infants who could not speak for themselves. So in summation, if you're just a bigot: accept it, understand it, and embrace it. But don't cite anything scientific bc you sound dumb.