To put this post in perspective, a pastor from a church my family attends recently said "the Reformation caused the Crusades". This sounded horribly misinformed to me, but my knowledge of medieval history isn't really enough to articulate why this is wrong.

I'm wanting to write this person a letter explaining why he was wrong (he might not be but just if he was) and give him credible sources so he can learn something as well.

I apologize if something along these lines has been answered before in advance (and for any formatting issues, I've never posted on here before) Thanks :)