I posted in the Exchanges that Make Your Brain Hurt thread about my coworker I'm calling Granite. Granite is a nice guy, and good at the parts of our team's function that he's responsible for, but he doesn't understand the other parts (which I am partly responsible for) as well as he thinks he does.
The problem is that when he misunderstands or doesn't understand something, he'll argue about it until he's blue in the face. I don't know if we aren't explaining things well or he's just being dense, but this always results in the team going around in circles, us trying to explain in increasingly simple terms and Granite missing every point we throw or deflecting it because cuss it all to tarnation, he's right, the sky *is* green paisley! Friday's meeting was supposed to be half an hour, but it dragged on for more than an hour because no matter how simply we explained things, Granite either couldn't or wouldn't accept that he'd misunderstood how the piece in question works and the functionality he was trying to shoehorn in was completely out of our scope. It's interfering with my work because it wastes time that I need to complete my components, and it's gotten so that I cringe internally every time he opens his mouth.
So, I guess I'm looking for a polite, professional way to tell Granite "You're holding up the meeting. Drop it because we have work to do and I want to get my component built before midnight!" I know I can't flat-out day "No, Granite, you're WRONG." and I can't just brain him with my notebook and be done with it, as tempting as it is. Hopefully it wouldn't be too unprofessional to just say "I have to go work on my green flibblewobbles now" and leave when he gets going.