You can’t reason with a group like ISIS/ISIL. Regardless of the surface trappings, violent extremism like that can’t be stopped with humanitarian aid. History is a cruel teacher, but it’s shown us time and again that the only effective resistance for wanton cruelty and violence is the precise, targeted application of violence by a relatively just nation.
It’s like a rabid dog. You don’t kill it because you enjoy killing, you kill it dispassionately and professionally; by killing it you make the community safer.
Tl;dr – some folk just need killing.