An accurate name is not a derogatory name.
Addressing Bruce Jenner as Bruce, or calling him a man, is the first step to honesty, healing, and restoration. He is not a woman. It is a wicked, barbaric, harmful lie to affirm him in his mental disorder.
The most dehumanizing thing you can do is say "Well, if you're happier hacking off your own parts because you're mentally ill, go ahead. It doesn't affect me. Here's the knife. I'll make sure insurance covers your self-mutilation." That's not kindness.