The Crotch -- not quite sure how the counter argument writes itself. A comparison of these cultures will find complex differences in morality, which is true, but there are a great many axioms which will be found as common to all human beings on the planet across all cultures -- i.e. a universal morality. Then again, like God, this is a concept that still requires a certain degree of faith to be able to follow.
I'm a Christian, and after reading Collins' book and Mere Christianity, I find them both interesting defenses of God, Christianity, etc, but they all do require faith or a fundamental yearning for something beyond onesself in order to succeed at convincing the reader. So, one who goes into it without that yearning, even on a very minute scale, will gain nothing from these books. I love these books and find them to be fulfilling, but they're not defenses of ones faith.
Faith in and of itself implies that you can't prove it. You can't prove that God's real or that Jesus walked the Earth, but you know it in your heart and have faith that it's true. Faith is blind, by definition. Nothing can really disprove ones faith -- heck, even proof of different ideas can't necessarily disprove it.
Proof of multiple deities, that Jesus was married and had children, that the resurrection of Christ didn't happen, etc. If these things can contradict the faith of a Christian, then they're faith wasn't that strong to begin with. Then again, this is coming from the Evangelical Christian who believes a) in a more henotheistic viewpoint of the universe whereby other gods may exist, but I worship the god of Jesus, and Moses who says He is the God above all others, and I believe it; b) that all people can be forgiven and be accepted into Heaven, regardless of religious background because any god which would preach and discuss a faith that has as a central tenant forgiveness, could not condemn a person that happened to not be born in a region where its faith isn't practiced; and c) Genesis isn't remotely translated correctly and it'll take a long time before we actually understand how the first followers of the Hebrew/Christian God lived, it's pretty obvious that there were more people than Adam considering his son Cain went out and met others...who he had never seen before...and were not his relatives. But, I'm a far cry from your average Christian on the street...
I've also found, on a slightly related note, that those who become the most obnoxious in defending their faith, are the ones who really need to prove it to themselves...