How do you deal with really obnoxious, know it all dorks?

I had a group for one of my cles, and there was this guy in it who was just a complete moron. We were supposed to work as a team to brainstorm ideas for a business plan. Every idea I said, he shot down. I even came up with an awesome idea that everyone else liked and he basically said NO we're not doing that. He kept saying we had to be creative and innovative, yet his ideas consisted of a taxi service and a diner.. hmmmm.. I think those both have been done. How do you deal with an all knowing, pompous jerk like this? Do you tell him off, or just let him think he's right and ignore him? Or kick him in the nuts? LOL