For some people, they'll be shocked by your assertiveness, and if you say something clever, they may even learn something.
But then some people won't hear the content of your response, all they'll know is that you said something "rude" and go on hating us trans people just the same.
And then there are some who'll feel bad about what they said if you respond in a kind or forgiving manner.
But then others will perceive that kindness as weakness and go on hating us just as much as before.
So it's a real toss up... What to do? I myself would just get out of that situation.

run away!!!!!