I don't think anyone is really debating how bad and evil ISIS, Al Quaeda and these other groups are. The debate is why the U.S.? Why Europe? Why not let the gulf states and the regional powers deal with this problem? Why attack these militants and make our countries targets? Why waste further billions when we are trillions in debt?
There are larger geopolitical objectives here at work most surrounding control of oilfields and the ability to eventually build a pipeline through Iraq and Syria reducing EU dependence on Russian pipelines.