Probably so but its too bad if he doesn't accept because it would be great entertainment. There is value in that.
I think an argument is way more credible when it is tested.
A man's work might be interesting to read but how how credible is it? Should we buy what he is preaching simply because he said so? Lets test it against the opposition and see what happens.
Oh, absolutely. It'd be a blast. Personally I suspect if Dawkins accepted the challenge you might be rather surprised as to how the man acquitted himself, but that's just me. I agree, however, that a stand-up test is preferrable than just letting a book do the talking.