I've gone into this on a previous answer about Thomas Madden and the idea of the 'defensive' crusade. In the later 11th century, there were growing concerns across the Christian world about the advance of the Seljuk Turks, and increasing danger to pilgrims as a result of regional warfare in the Levant.

I also answered a similar question recently, although it was about the First Crusade specifically.

(In brief, was the First Crusade a defensive war? Some participants thought so, but there were many other reasons people went on crusade.)

Some of the other crusades were launched in response to a recent event - the Second Crusade came after Edessa was conquered in 1144, the Third Crusade was after Jerusalem was conquered in 1187, and the Seventh Crusade came after Jerusalem was lost again in 1244. I guess you could consider those "defensive", maybe...