Although you're trying to isolate the discussion, we can't escape the fact that the only reason we're talking about transrace is because it's being wielded in defense of Rachel, whose story is being compared to that of transgender people. That comparison is most often an act of bigotry, meant to belittle the lives of real, breathing transgender men and women rather than to uplift transracial people, whom you admit only exist to you theoretically.

>once upon a time there was no such thing as a transgendered
>person
>walking around. People are using everyone from Tom Hanks'
>son, to this
>NAACP woman, to Tiger Woods in this post to make varying
>points about
>'transrace' - but it's a theoretical discussion - of course
>hypotheticals are
>being discussed.

But there have always been people who fit the characteristics of transgender people. Transracialism has been a recognized thing for a while, but not in the way that you are defining it. I think that when you look at the specific cases of people who adopt transracial identities, it becomes more evident the ways in which race and gender, although both social constructs, operate differently.

>not sure how that 'gotcha!' moment would work for me as a
>heterosexual
>male, because I have nothing to hold over LGBT folks' heads
>except
>their constitutional, human, and universal rights.

I don't doubt that your heart is in the right place, but in this post, the people on your side are hetero men who have previously expressed negative attitudes toward transgender identity; men who I think are opportunistically looking to strike back against the marginalized people who've challenged them in the past. Their participation, and the context in which it has arisen, makes it hard to trust the sincerity of this discussion.