Thanks for your reply. I'm not sure about "toast". The question would be one of evidence and how the discussion was framed. If the professor noted that the consensus is still emerging and provided peer reviewed evidence to this end, I would think that would be fine. I see no problem with explaining how there are still questions to be answered and even with noting what standard of evidence would result in "proof" for the scientific community. 

If the prof instead says, "well you look like a man to me, so I am going to ignore what you want to be called and do whatever I like," than that is a different issue. Then it becomes one of respect and yes, human rights. 

Arguments supported by evidence = A-OK. Arguments based on ignorance and personal preference aren't. i.e. What prof could use the N-word, b/c free speech? Or the C-word? 

Please note that I am not accusing you of the above, nor of being ignorant. I simply explain why "free speech" does not work for me in this instance.