I haven't been further involved in this thread because it spirals to pedantic debates. Let's not gloss over the tragedy by trying to find reasons behind the actions of evil.
There are many sects of Islam, and there are ones that are not even recognised. I am a muslim, of the Ahl Sunnah Wal Jamaah branch. We adhere to our roots but sometimes adapt from the good and beneficial teachings of Hambali, Maliki and Hanafi. We have been taught, as part of our civic and moral code of faith from early childhood to never hurt a single ant, let alone a fellow human. When we are wronged, we are to do good on those who wrong us. I can assure you that those of my branch of which there are millions will not be easily indoctrinated because of the early civic and moral guidance that were given of us.
This is not a religion issue. This is the lack of education on one's religion issue.
I don't know how others here are opinionated that the book and its teaching has caused this. I can recite the book many times over but it didn't and will not ever drive me to performing or justifying evil acts. It's not the book but the people who manipulate its words that is of a concern. If someone has been given the right foundation of Islam from early childhood, they will not seek the 'expertise' of others in early adulthood, because their proper immersion of it while growing up gives them free will to decide what is right or wrong. When I turned 12, which is the average age of completing formal religious education, I have more than enough in me to discern what is right from wrong. We do not have to seek the purpose of living anymore as the religion is so integrated and seamless we can be part of the community as normal people. We become dentists, doctors, lawyers, football club owners, footballers, etc.
The trends with many of these individuals can be easily recognised. These are people without access to the right people in islam to guide them. The right system to direct them. These are people who already had unstable moral and civic upbringing hence were easily swayed by interpretations that do not reflect the truth. I can tell how easy it is for those who have not been immersed since birth in proper Islamic teaching to interpret the religion wrongly, by reading this thread alone. It is so easy to misinterpret something that you haven't had the chance to properly learn in time.
I know that there are calls for us muslims to act on this. But please understand we are in the same boat as you are. What are we supposed to do that others cannot do? We are as detached from these people as you are. My teachings cannot relate to their actions at all it is as different as night and day. People can cite excerpts from the book all they want but I've read the book millions of time in my life, and never once has it swayed me to do evil. If the teaching is right, the interpretation will be as well.