You CANNOT be that thick.
A guy says "I'm a Duke AND UNC fan." On the face of it, that sounds ridiculous, and makes people laugh.
I respond with a question that, you would think, is THE definitive question that will show what school they are TRULY a fan of, a question most of us already know our own answer to and which I think ALL of us would be a pretty good indicator, because there is not a single Duke fan who thinks UNC is innocent and there is not a single UNC fan who thinks UNC is guilty. I even insert the possible Duke and UNC responses, without any judgement, and then add a faux UK response (because they focus on UofL) and a faux South Carolina response that plays on their overwhelming confidence, aggression, and frequent use of the term Carolina.
If you really don't see that the whole thing was meant to get a laugh, I can't help you. I have a feeling that the only fans who will get upset by that and take it seriously is UNC fans.