Even though ISIS had been threatening "Nazaranes" (Christians in Iraq) in Mosul with expropriation or extermination unless they renounced their faith, this had not moved the Obama White House into action.
A fortnight later, 40,000 Kurds who practice the Yazidi faith were herded onto Mount Sinjar and left to fend for themselves or be slaughtered. Yazidis have a monotheistic faith which has roots in Zoroastrianism with elements of Islam as well as Christianity.
What may have prompted President Obama to act in the case of the Yazidis rather than the Iraqi Christians may have been concentrated the ethnic on a mountaintop for genocide and then bragging about it on Twitter. Or perhaps it was ISIS terrorists putting Yazidi kids' heads on a pike as a message to the world. Nonetheless, former Governor Mike Huckabee has it right, it is evil