Ah, I got it.
That’s something I’ve been working on with little success — how to exit the circular, accusatory conversations. When I try, he follows.
We have a couple of “safe words” for taking a break or exiting conversations entirely but he doesn’t respect them. He either just follows me or pulls me back in (again, acting reasonable). I’m ashamed to say I’ve let him. What I need to work on is standing my ground and just refusing to participate. Obviously a work in progress.