Not denying all the excesses and abuses (and stupidities, treacheries and cruelties) -- but keep in mind that the Crusades were defensive. Built on the early preaching of the original Apostles, Christianity had extended from Mesopotamia to Gibraltar by the arly 7th century. The forces of Islamic Jihad invaded and occupied fully 2/3 of Christendom with fire and sword and was threatening the very walls of Christian Constantinople.
It was at that point that the Byzantine Emperor urgently appealed to the West for help.
The point was never to convert the Muslims by force. The point was to defend the Holy Places and the Christians of the Easr. For an excellent, short and accurate summary, you can read historian Thomas Madden at:
http://www.churchinhistory.org/pages/leaflets/the-crusades.htm
This can't be pointed out often enough.