Don't forget that the KKK are extremists as well.

I think the pool is running even because often the two are equated in the media. I tend to associate extremists with fanatics, while fundamentalists could just be someone with rigid beliefs. I think the extemist are the more dangerous, as that is where you find most fanatics who are the really dangerous ones.

Doesn't matter which religion, (or political cause) fanatics are the dangerous ones.

Neither and both. I think violence is committed by people who are angry and want to control and gain power through as much destruction as possible. These people have been damaged and use religion and politics to their advantage to enlist others into their cause.