Yeah, it sounds like he's crossing a line.
I have been to two massage therapists, both female. The first was ok, the second was wonderful. I found her through referrals from the first one when I moved from one town to the other. Ask around and look for a new therapist. I don't think he's going to be able to repair this damage, if he hasn't sensed it by now.
In the meantime if you do go back you may need to be very clear about him not talking about this. Try saying STOP to get his attention, sit up if you need to, and tell him to stay off that subject, period. If you're not comfortable confronting him (and I guess most people wouldn't be) then you probably should just not go back at all, back pain or no back pain.
Also, this may be the time to see if you can find some sort of exercise to reduce your back pain and prevent it from recurring. Not that you should give up massages if you have an RMT you're comfortable with and can afford. I miss those massages.