I think my therapist is transphobic
Are you really sure they are transphobic?
Maybe but I know not all of them are.
You are only making assumptions, and that is hurtful to them and your image of them. They couldn't be a wonderful ally and you don't know it because you're just judging them all the time. Just be up front and ask them what do they think.
Are you suggesting that I let them tell me they are wrong and make a fool out of myself?
It is pretty serious to accuse someone of being hateful to others. They deserve the chance to explain their views you might be surprised by what they think.