In school when I learned about "the church" it was all negative. If you ever wonder why people view Christianity as such a bad thing, well it's because they have to come to that conclusion considering the facts they are given. I learned about the manor system, the Crusades, and never about Christianity's contributions to the world.
I was taught that the Crusades were a bad thing...an attempt by the Church to consolidate its power.
However, considering all we are learning of Islam lately, I am beginning to think (although no martial effort is without collateral damage) that the Crusades saved Europe from a scourge worse than the Black Death.
As far as the Crusades go, please take a look at this article and re-orient yourself as to what happened and why.