"...for whatever dark reason..."

Have you considered the reason may be, partly what the Quranic movement promotes? Have you read the Quran, the book promoted in mosques? There are many distasteful tones and messages. For example, here's one explicitly asserting that Muslims avoid befriending Jews and Christians:

Quran 5:51
O you who have believed, do not take the Jews and the Christians as allies. They are [in fact] allies of one another. And whoever is an ally to them among you - then indeed, he is [one] of them. Indeed, Allah guides not the wrongdoing people.

Islam is not just another 'great' religion, it is not a benign movement vis-a-vis a judeo-Christian SECULAR culture.  

if a Muslim quotes the (in)famous 'no-compulsion' verse (2:256) please note that it is followed by 2:257 - where we're told non-Muslims will burn in hell.  

This in no way condones the murders, I'm just suggesting that people be aware of what values the Quranic movement is promoting.