Your attempt to argue this is somehow vague or a slippery slope is silly - most workplaces seem to have not a tremendous amount of trouble with this, even though it is not rigorously defined.
Wait what
that said, "transgender lesbian" shouldn't be too hard to parse unless you've been living under a rock for the last fifteen years.
A transgender lesbian, therefore, is a transgender woman ("male-to-female") who is attracted to women.
"lesbian" is not a "sexual attraction" description, it is an "attraction description" for which one possible dimension of attraction can be sexual. Same-sex attraction is no more exclusively about a desire for intercourse than opposite sex attraction. It's entirely possible to have a romantic attraction of any kind without also feeling a desire to engage in intercourse.
I shudder to think about your love life, if you solely define your relationships on sexuality alone. Sexuality is a step from an emotional state to a physical expression of that, of course outside of prostitution and casual hook-ups. And I don't mean that in a negative way, I just...feel sorry for you.
All of these are regular everyday things for me, but I've had people tell me that even asking for basic respect is "disagreeing with their political opinion". The real problem is where the line is drawn, or whether a line can even be drawn.
The comments about being dependent on one's sexuality, or 'making it up,' and thusly being prepared to accept being mocked, are particularly disturbing.
The inability to separate a romantic and sexual nature is more so just surprising.
Very eye-opening responses for me.