How can you say not all Muslims are extremists when their own religion tells them to murder in the name of Allah?
To put it simply, because not all Muslims are extremists. Because they don't undertake extremist acts. If it neither walks like a duck, nor talks like a duck, it can't be classified as a Muslim extremist. (Or duck.) Are those elements in the Qur'an? Yes. No one's denying that. Do all Muslims follow every word of the Qur'an? No. Because, like Christians, they pick and choose which parts of their holy text are applicable to their lives. Unless, of course, you're advocating that we start stoning adulterers.