I'm so sorry. Many people harbor these kind of beliefs and just keep them to themselves. Cracking open a door into someone's heart and finding darkness there is always devastating. I've been betrayed by a lot of people this way - people who are ready to smile and make nice but secretly think you're delusional and that trans people just decide to be trans so we can get attention (oh, we get attention all right - the bad kind!) and be professional victims or some such bullshit. These people are deeply insecure and angry - possibly even resentful - when they see trans people thriving. Like all bigots, they are projecting their own emotional baggage onto you.

Unfortunately, we can't control other people's behavior; we can't force others to rightfully embrace love. We can only control ourselves & our own reactions. If you feel it's safe to continue associating with this person, and you want to do so, you can attempt to educate them (with the caveat that this will be a soul-crushing experience regardless of whether you change their mind - and you may never change their mind). Otherwise, you should distance yourself from this person and aggressively tend to yourself and your spirit during this time. For every bit of pain you felt finding out this horrible truth about your friend, love yourself tenfold. Love yourself in spite of this. Love yourself a thousand times more deeply for hearing this. Seek out joy & comfort from friends and activities that enrich you. Allow yourself to grieve the relationship you thought you had with this person, and then strengthen the relationships of those who love you for who you are.

Take care of yourself now and always, my friend. Sending love & light your way.