I either came up with canned responses (that I actually had to practice) or pretty much just quit talking to him about it. My xah knew what the problem was. He just didn't want to admit it to himself and he thought he could manipulate me out of my decision by continuing to ask and argue.
So be it if he didn't understand. I finally just started saying "I'm sorry about that." if I felt I must reply for some reason. I wrote a couple of letters didn't really further his understanding any but it gave me peace of mind because then I could say to myself "OK - I said what I wanted to say in as clear a way as I could and I gave it to him and now I can be done with that."
He claimed not understanding, not getting it, not who he thought I was, for a year after our divorce. He didn't stop doing that until this most recent stint in rehab. His counselor asked for a conference call, and I agreed, and maybe they helped him understand or move past that. I don't know. Maybe it will change if he relapses again. Either way, I just had to let it go. I no longer spend time wondering if he is manipulating, really not understanding, or what else. I just move on.