If they can, they should retreat. Yes, they should flee.
If they can't do that, I have no doubt they can hold their own until reinforcements arrive. After that, they should leave.
"I am not among those who fear the people. They and not the rich, are our dependence for continued freedom." -- Thomas Jefferson, 1816 "[F]acts are before ideas." -- Mikhail Bakunin, 1882
Here is just one case.
BBC News - Jihadis accused of new massacres in Iraq and Syria
IS is also accused of killing 700 tribesmen opposing them in Syria's Deir Ezzor province, over a two-week period.
If my post offends you, I deeply Apple-O-Jize.
“Capitalism is the astounding belief that the most wickedest of men will do the most wickedest of things for the greatest good of everyone.” John Maynard Keynes