ISIS attracts the worst sort of people because they can do the most evil things imaginable and get the blessing of their imans when they do it. Every member of ISIS needs to be hunted down like the animals they are.
Yet another opportunity for me to say this is an example of why Islam should be strongly discouraged in our prisons. Violent convicts have already proved what they can do. Islam, in exchange for a little discipline in victim selection, gives them a rationale and authorization. It does the opposite of what religion is supposed to provide in prison--a moderating influence.