Who is stifling the debate?
Not "who" but what - and I believe the answer is fear.
Fear of becoming the next target of the trans-activists, who shout loudly, make threats, and rally public opinion.
The Tara Hudson case is evidence of that. The judge sat on the fence, and the professionals who are employed to apply policy re-interpreted that policy in response to public opinion, and in doing so, disenfrachised the less vocal majority.
Far better that the debate doesn't happen, than organisations such as the BBC having to take a stance and alienate one or other of the "sides" of the debate.