It's not up you how somebody wants to be addressed after requesting it. You don't have to harbor cruel feelings about it. Singular they has been used in English for a long time historically.
Really? If you were to ask me to address you as Your Imperial Majesty, you should not hold your breath waiting for me to comply.
Language evolves; in formal English, singular they has long been unacceptable. (Informal English is another story.)
EDIT:
>You don't have to harbor cruel feelings about it.
You're proving my point in assuming I "harbor cruel feelings" about trans people.