What shocks me here is less the portrayal of trans people and more the fear of Sanji. And I believe this fear is much deeply rooted than we may think.
I've been a strong advocate of the idea that Sanji has been pushing down a part of himself, something that was let free here:
To what degree.. I don't know. Perhaps it's something else, but I think his self-sacrificial behavior is partly bonded with a deeper belief.
Oda rarily do things without a purpose.