How to Keep on Topic When a Guest Makes a Whacky Statement

How do you keep on topic when the guest makes a far out statement? Some of the things that i've heard make me smile from time to time. But my rational journalistic side says, well, here's a good story. It isn't me to determine whether it's true. All of us can have an opinion. But that's probably, unless we have definitive, documented or photographic proof, that's all wean we can do. If you don't accept it, or you find it annoying for whatever reason, got to turn it off.