You run into the same problem with lots of Protestant sects. It's probably one reason Luther found it necessary to edit the Bible somewhat so as to better comport with his personal interpretation.
So, at that point, it's just a matter of discerning which of Islam's groups have the interpretation most closely aligned with what other believers (and non-believers) would recognize as "Self-Evident" or universal truths.
It's not JUST that the take of these so-called "radical Muslims" is abhorrent to all ... it's that their "consciousness raising" tactics and clearly materialist and hateful mindset reveal them to be the product of a more insidious "organizing". Despite the overlay of "Islam" under which they operate, they've far more in common with the rest of the world's radicals -- IRA, Black September, Weatherman, Black Panther, Shining Path -- than they do Islam.
That's because they're communists -- militant ATHEISTS -- masquerading under cover of Islam.
The beauty being that -- as with the co-opting and revolution from within of the Church (where the revolution works inversely ... turning heretofore Christian Soldiers into "peace and justice" pansies whose battlecry is "Tolerance!") -- there's a sucker born every minute and plenty of Extras ready to latch on to give the militant atheist top-down vine of organization and control the followers necessary to mask it with "grassroots".
I'll agree with you to some extent, but Islam has always been a war-like religion. il-Ilahi [moon-crescent] was the greatest of the 360 pagan gods of Mecca and Medina. Ilahi was a war god--god of the sword, of the bow and of the arrow. In order to build his religion Mohammed abolished the other 359 lesser gods, leaving Allah [the pagans term for a monotheistic god].
I got flamed for saying this on another thread but you can trace the roots of the violence back to Genesis 16: 11-12.
11 And the angel of the Lord said unto her (Hagar): "Behold, thou art with child, and thou shalt bear a son; and thou shalt call his name Ishmael, because the lord has heard thy affliction.
12 And he shall be a wild ass of a man: his hand shall be against every man, and every man's hand against him; and he shall dwell in the face of thy brethren.
They have always been war-like and are perpetually at war with everyone.