Part of the problem must be one of not knowing what is really going on in that region. We in the West have been lied to by media and government time and again about what is happening in the Middle East (think 9/11, Iraq, Afghanistan and others). Maybe ISIS are as bad as the Western media say they are. But perhaps the full truth will only come out in many years hence when we might find (it is possible on past performance) that certain Western agencies have planted false scare stories in the media, that we were not told significant facts about the funding of ISIS (by the West) and the group’s manipulation by the West for its own purposes (toppling Asad) and so on.
Muslims are often sceptical about a usually pro-American zionist media. And rightly so. Maybe the best position is to be agnostic about what is happening until we get all the facts. But that may take years.
Give these factors I’m not surprised Muslims are not signing up to Western armies to fight ISIS. The West must stop invading Muslim countries, stop supporting dictatorships, stop funding extremist groups (like ISIS), and get the hell out of there. Their presence is extremely destabilizing and leads to bloodshed.