Islam is a young religion with many temperamental members. Christianity was like this, in its day. Except it didn't grow up in the shadow of its predecessor.
>implying fundamentalism deserves justification
There is an enormous, silent majority of moderates who want nothing to do with the violence.
That's only the terrorists, not the Muslims. If you imply otherwise, twisted "Muslim" terrorists (who misinterpret the Quran) will kill you. Real Muslims won't.