Violence begets violence. As true a truism as there is.
The worst part of this aside from the immense tragedy is that is seems as if a new ethnic group will now be pulled into civil war in the Iraq. I also wonder if since the Yazidi are Kurdish speaking, Iraqi Kurds will interpret the attack as an attack on them. From what I understand, Kurds have been mostly spared the ethnic cleansing and death squads that have been visited on both Sunni and Shiite alike.