Kaku is trying not to offend his host by redirecting him instead of outright correcting him. It's funny stuff, but he should take the more direct route that Dawkins takes:

http://www.youtube.com/watch?v=Z-FaXD_igv4

If you don't tell them outright they're just wrong, they take it as default evidence that that even if you don't agree with them, you at least don't disagree with them.

Still, you're right the dialogue is civil - and torturous for Michio.