That would just make it even more bizarre. Besides, Bob backed off on that when challenged and restricted the discussion to just US law. I think his arguments were better when he narrowed them down to America. It was more appropriate to Colmes' book, too, which was the reason for the interview, I think.
He should have started out with the "Jesus was a liberal" thing and stayed there. That's more Bob's ballpark, IMHO. Going after the history of laws against adultery in the US gave Alan the chance to challenge all the old laws we've since, quite rightly, gotten ridden of, as Bob agreed. Besides, it was a red herring to begin with. He couldn't get Alan to agree that liberals condone adultery anyway.
Nope, he's a christian preacher and he should have stayed on target with Jesus. It'd have made for a better interview and given Bob the chance to work from a stronger position.