According to several sources there are about 1.5 billion
Muslims worldwide:

http://en.wikipedia.org/wiki/Major_religious_groups

I don't think anyone actually knows how large the radical
Islamic movements are but there have been many estimates and
they exist in all major Muslim populations e.g. Muslim Brotherhood
(Egypt), Hezbollah, Al-Qaeda, Taliban etc. etc.

Since the worldwide population of Muslims is so large even a
fraction of a percent participation means hundreds of thousands
even millions of followers...

0.1% of 1.5 billion is still 1.5 million people.

And, the followers of the above radical movements believe
it is OK or even honorable to kill innocent women and children
to advance their cause. They use tactics like bus bombings,
airliner hijacking and crashing into public buildings, and random
untargeted missile launches into civilian population centers.
That is why all civilized and moral people must work actively
against such tactics and groups. But that still does not mean
that almost all Muslims are not lawful, peaceful, moral and
honorable people, they are and many are shocked and disgusted by
any perversion of their religion and acts of violence done in
the name of Islam.