Well, he clearly wants his guest to, y’know, oppose gay marriage. What’s the point in having an anti-gay-marriage guy on your show if he’s not going to oppose gay marriage? And you can see his visible annoyance at the guy–because it’s bad TV.
Apparently BO’s guest hadn’t planned beyond stating that people don’t want it and the rest of us slapping our heads and exclaiming, “Oh my God, he’s right!”