How do I get rid of Davey’s Sniper?

Hello Mr. Dan: I have a question for you about dealing with a guy in my office whose business is being mean. He is always sniping at people, and won’t back off. There is one guy in the office who this sniper guy hates, apparently. This very timid guy named Davey is always the butt of this sniper’s comments, to the point where this snide guy is now referred to as Davey’s Sniper. Really mean SOB. Anyway, today everything went too far for me, when Davey’s Sniper turned to me and slammed a presentation I’d just made to the executive board. He did this in front of the junior office staff–six of whom I supervise, btw. I asked him if he was meaning to insult me, and his response was: “Let me be clear, Shania, your presentation made you look like an unprepared moron.” I was so taken aback I didn’t know what to say. Most people like this guy back off when you assertively confront them, but Davey’s Sniper just won’t quit. Apparently Davey’s Sniper is a special breed? I never want to be called a moron again and I never want this guy on my back again. HOW CAN I SHUT HIM DOWN? Davey’s Sniper is very intelligent, by the way, and I’m not looking for a debate from him. PLEASE HELP ME, DAN!

Shania