I can certainly respect his opinion, but I would just like to say that I really, really hate it when people try to refute Christianity by bringing up:
1. The Crusades
2. The Spanish Inquisition
3. The witch trials
This is not an especially good way to argue the case against Christianity, and, ironically, people who use this kind of rhetoric generally end up looking like bigots even as they are preaching their messages of tolerance and inclusiveness.
I hate this, too, because those three things always make me think of Monty Python instead of the subject at hand. =D