Anyway. This may be offensive to some.

What religion isn`t man made? I don`t understand the logic in the Muslim`s argument. His argument requires for one to assume that because a fundamental belief in Islam is that prophets are a descendent from God, that they were indeed descendents from God. Now who is to disprove this? No one can prove or disprove the existence of God, so it is fallacious to carry on a religious argument in which one must assume the existence of God at the behest of another religion`s text written by man. The very thing you are forced to assume is the improvable factor in the argument. Anyone who says "your religion says your gurus were only men. The prophets in my religion were descendents from God, so my religion is Godlier/better" detracts from his own rational credibility.