Well, that's stupid, but at least he recognizes that a specialist may have its place.
I do not want to try to give instructions or directions. I haven't been through what you, or the others here have been through/going through. I just want to offer what little support I can and say it's heartbreaking. Your sister went and told her before you got the chance to, right? I'm not a very good christian (or one at all, hey), it takes strong faith to love even those who betray you. It's funny how the true believers always end up victimized by those who tow the line and ignore the actual teachings. You've got a hell of a struggle ahead of you.
Here I go giving instructions anyway. Be calm, rational, and concise when you talk to the therapist. Presentation is everything. If he lacks the experience of dealing with TS, beg him with all due respect to transfer you to a specialist because of the severity of the situation with your family.
However... finding a specialist might be hard. I don't think this site has one listed except like 200 miles away from me. I doubt your parents will want to take you up to dallas or san antonio. but hopefully someone near you has experience dealing with it even if they aren't a specialist.
May God soften the hearts of your family. Sadly, I don't think they'd know it even if he spoke to them.