Comment: This is embarrassingly easy.

What evidence do the transgenders come forward with to make the claim that they are the other gender, or that they want HRT or gender "re-assignment" (the use of this term with rational people would by itself stop the discussion and start the laughter)?

What evidence?  

Self-reports.

Do they come in with genetic data?  Do they come in with any biological data?

No, they come in with self-reports, at best. 

Tell us, John, the fine details of "gender determination" without waving your arms and saying "it's complex" (and throwing in the word epigenetics that you learned last week), with of course the requisite concomitant arm waving.