Remember that in the middle, and late middle ages, the Islamic world was the advanced, progressive, cultured and tolerant civilization, far ahead of western Europe. Christian Europe was a place of endless war and bickering and of religious zealots.
Especially in Al-Andalus, under moorish rule, muslims, christians and jews lived peacefully together in what was perhaps the most advanced, safe and free place to live in the world, at the time.
It's not really about Islam or Christianity. Both holy books contain a lot of questionable, self-justifying violence. It's about the human beings who interpret and lay out the words. This, in my opinion, is one of the greatest problems with the abrahamic religions. The holy books contain so many contradictions and inconsistencies, you can justify just about anything by picking out the relevant parts that serve your cause.