The crusades and the previous religious wars between East and West were all part of a very brutal time. I don’t think we can either judtify or condemn them from our vantage point in history without making some judgements we don’t have the context to understand fully.

Islam and Christianity were happy to invade their own until their emplires started overlapping in the middle east and southern Europe.

Given that - Islam still needs some more of the reformation that European Christians went through a few hundred years ago.