It wasn't really much of a debate. Kreeft is not as knowledgeable about Islam, and ended up agreeing with Spencer in the end.
Spencer's case is simple:
- Islam teaches people to be "bad" (from a Christian/Western point of view)
- Those who are faithful are "bad"
- Those who are not faithful are "bad Muslims" (not faithful to their Muslim, err, faith)
There is a convicting story around the 40 minute mark. Quite nice.
I think their biggest problems is that the Magesterium has tied their hands. They have to say that Muslims worship the same God, and that by keeping to the light they have, they can earn salvation.
But this (Islam) is a problem that requires conversion. We must preach Christ crucified (a stumbling block to some, foolishness to most, and blasphemy to the Muslims). We must point out the doctrine of demons (as all false religions are) - and say that it is false; not muddled, not half-true. That there is one Way, not many.