Ragnorak: I would think of the kind of Islam the terrorists believe in to be a seperate religion to normal Islam, more like a cult in fact. There are always going to be people with murderous inclinations in the world who want something to unite around or justify their actions, so if it isn't a twisted form of Islam then it'll be something else.
rightly said, those ppl are extremists.. they don't spare the moderate Muslims.. they misuse ppl and religion.. that is not what Islam teaches us.. if ppl want to understand Islam, they shouldn't look at the black sheep of community.. but look at the scriptures.. malala yousufzai, the girl awarded Nobel peace prize is a Muslim.. who will label her as a terrorist..