@Cool Cat, I don't know how helpful this will be. My T often goes off on what seem like weird, "New Agey" tangents. That's what he did with this. (But there was definitely something there, as it happened.)
He says that he thinks everything our brains do at least begins as something adaptive. It might not be the BEST solution to a problem, but it's the solution it came up with at the time. He also says that he doesn't think our brains ever do things with the intent of hurting us, they are trying to keep us alive. When SI came up, that's what he said (again). I said that I couldn't see how this sort of thing ever would have been helpful. He said he didn't have the answer. That I was the only one who had it and I'd have to find it for myself. (I SAID he gets a little "out there" sometimes,) He said that some part of me knew the answer, I just had to get it to tell me.
This didn't happen over night, by any means. The answer, at least a good part of it, showed up one night in a dream. It wasn't what I was expecting, at all. but I could see the truth of it and could see how it weirdly made sense.
I can't honestly say that I never have those thoughts anymore. I have them less. When I DO have them, it's much easier to notice them and let them go. They've lost a lot of the power they once had. (And, I didn't give you the answer because YOUR answer might not be the same.)
I'll be very interested to hear how your T handles this. What ever the case, he's not going to MAKE you do anything you don't want to do. That would be counter productive.