And in that comes the great contrast with the successes achieved by the followers of Muhammad. Although it is true that the Muslim armies achieved some major military victories in the 7th century, a great part of the success in the building of an empire that soon ran from Spain to the Hindu Kush lay in the tolerance towards those of other faiths, by a softness of touch that came as a surprise to many.
People of the Book (Christians and Jews) had a special place reserved for them under the Islamic tradition – one that commanded respect and demanded safety. Early Muslim leaders built churches and showed respect for beliefs that did not mirror their own. That message has been lost by those willing to murder strangers and blow themselves up. There are better, and more enjoyable ways to reach paradise than through death and destruction.
http://www.theguardian.com/commentisfree/2016/jan/18/isis-islam-conquests-prophet-muhammad-religion