I suggest when he engages in the conversation again you say "I will do whatever my L recommends" and try to leave it at that. It doesnt matter that you are right. He will never (at this point) agree with you. He will seek out people that only agree with him. Take yourself out of the debate.
I totally agree w/ BK here. He will not like it but I think it's best for you to defer to your L.
Soooo sorry Purg, such a tough conversation and time to move through. We all have your back on here.