I think the biggest thing is not do what he says. In all seriousness though, I would definitely not start a "war" with him. Obviously he can say some pretty devastation things, I would not want to know what else he has to say.
I have in the past just blocked their chat, they get even more mad at that. It is like being extra polite to someone who is a customer and are being real snippy. If you are overly nice to some people it gets them mad as heck. I prefer being nice to people myself. You never know what kind of day the person is having and it just might change their outlook for the whole day, or even longer.
I have heard a lot about bots as of late, and some people get pretty mad about that as well. I think I would have just said at the start that I am not a bot, and I don't really appreciate being talked to that way.