So I said, "I sure hope that you are not IMing OW because that would be really disrespectful."
He YELLS back, "I'm on the damn internet. Then mumbles, shut the F up. I can't stand you." I almost lost it. Any advice on how to handle it? I really don't want to just ignore, but he's not going to continue to speak to me that way. After what he's done, he's speaking to ME like that?
Set a boundary and be prepared to enforce it.
When you XXXXX, I feel YYYYYY. I want ZZZZZZ. If you continue to XXXXX, I will QQQQQQQ. Then do it.