Because of the ethnic make-up of Iraq. Sunni Arabs are less than 20% of the population but were made the rulers in colonial times. That's why they have a history of savage violence - its the only way for a small minority to retain absolute power.
Same logic applies in reverse in Syria where the Sunnis are the majority and the Alawite minority retains absolute power through savage violence.
But doesn't that just help perpetuate the nonsense that a particular religion or ethnic group should be in control of a particular area on the map? The less we refer to their ethnicity then the less relevant ethnicity will become.
Wow! You really are into American power aren't you? You think that if Americans stop referring to a problem, the problem ceases to exist??
The Sunni militants in Iraq and Syria say that they are killing people because of their religion, so how you refer to them doesn't matter - they have set their own terms of reference.
Not at all. I didn't say anything about Americans or American power. Not sure how you came to that conclusion. I'm simply pointing out that it's not the fact that they're Sunnis that makes them evil. It's the fact that they are murderers that makes them evil and they don't speak on behalf of or represent all Sunnis.