As others have inferred it's all about sex, sorry sects. No, seriously, the Muslim world is as diverse in its religion and practices as Christianity is, all mainly due to early history and interpretation of the Koran and the various Haddiths. I am sure you are more than aware of Shiites, Sunnites, Wahhibis but then there are Sufis, Ibadis, Hashemites, Kharijites, Ahmadis and several others.....different practices, 'health' acceptance, leadership structures, etc, all akin to what happens in the Christian domains.
And one last point, in my experience, the large majority of Muslims abhor the extremism and violence that a few practice or extol - aren't Christians the same - a few quick thoughts about Northern Ireland should underpin that comparison.............Understanding the drivers, the commonality in practices, and differences is the key, ignorance between us all so prevalent in both religious communities.