"Are we not talking now?"..and I'm not sure how to respond then. No response right?
I am not sure about this but my thoughts are. We are getting D. Why would I want to talk to you? Why do you want to talk to me? You are D me. Maybe just the first sentence and end the conversation.
He needs to understand what his actions are causing and your actions need to respond. The NC is a form of communication. It sends a pretty clear message.