That's a nice catch. "You still have doubt in your heart". I thought the tranny was specifically referring to doubts about his sexual identity (not necessarily his sexuality though).

It would be pretty sweet if Sanji learns to release epic haki after finding and reinventing himself as a tranny. Maybe he'd even come to realize female villains are still villains. And the Sanji + Zoro interactions would reach a whole new level of funny. Sanji has always had a bit of a "dramatic" attitude with Zoro.