I think Vik Rubenfeld at “The Big Picture Blog” said it best in

The REASON(S) for the Crusades –
http://www.bigpicweblog.com/exp/index.php/weblog/comments/reasons_for_the_crusades

It is hard to imagine that the competing European Powers couldn’t set aside their hatred of each other long enough to extinguish the Piracy and Slavery. Same old rivalries in force today, Until finally U.S. elects another Jefferson and Madison …