I agree, but let's acknowledge that for now, we have the privilege of commenting on this from a land that is not torn by jihadist strife. We don't know what it's like to see our neighbors, friends, even family members marched off to mass graves by those who will brook no religious disagreement.
These are not people who can be imprisoned for a time, while we destroy their political infrastructure. Every last one of them, eventually, must be eliminated. SOMEONE is going to have to engage in a bit of savagery to accomplish that.
I do understand that the guy was likely driven to it by very personal experiences. It is still the wrong decision. Over and over I have heard the point made that it is Muslims committing savagery and no one else. Keeping that true is very important. ISIS commits atrocities even against other Muslims. The entire world needs to be against them. If Christians join in on savage tactics then in the long run, they harm rather than help the war against ISIS and their kind.
You never win by become just like what you are fighting against.