What I think

I have visited lot of countries, met a lot of people because of my profession. Every one asks why are extremist doing the things they are doing.
I do not have all the answers but this is what I think.
The culture in Pakistan is diversified so many people living in the same city have different language, ethnic and religious background. Every where people have differences over small things as whether to fold your arms while praying or not to big things like calling each other infidels and non-believer. In a developed society such differences are mostly solved by dialogue and even if they are unsolved nobody forces others to follow his/her ideology.
In my country we are arguing on such matters for so long that now either we try to force it on others or disconnect with them on social level. There is no solution to these differences as each have different interpretation of Islam Qur'an and Prophet's teachings.

I think the basic reason for Islamic extremism is that when it comes to religious matters everybody is a scholar and chooses to follow the part of Islam according to his liking. Add illiteracy both modern and Islamic and you have dangerous mixture.

I also think that poverty and social injustice are among the main causes of Islamic extremism.
I once had a chat with a potential extremist. he was a learned fellow, polite with other people but his views on the Muslims and there general conditions in Iraq, Afghanistan and Kashmir were a bit " extremist ".

My point of view was that we should solve these problems with dialogue but he was in the favor of using force.