Why do people on this forum care about ISIS and want the US to get involved with drones or whatever? Iraq is a very violent place. The Sunnis have been slaughtering everyone else there for a long long time. Just because its being recorded on cellphones now doesn't mean its new or worse - Saddam Hussein had several years in which over 100,000 prisoners were killed.
Why do you categorize these murderers with the label "Sunnis"? Do you think all Sunnis approve of or are responsible for these crimes?
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.