We can be idealists. We simply cannot be starry-eyed idealists and expect good results. Sometimes we really need the mailed fist behind the velvet glove as foreign policy. When we deal with Nazis or ISIS we need the mailed fist. Moral suasion against evil persons and causes never works. We cannot assume that similarities of culture (Nazis never spared Jews for being Germans by culture) or the shared tenets of religious faith (ISIS is killing plenty of Muslims) can give us common cause. War crimes and genocide forfeit any claims by a side to defensible virtues.
As there was nothing hypocritical about loving Beethoven and hating Nazis in the last Crisis, there is nothing hypocritical about recognizing the virtues of Islam and hating ISIS in this Crisis. Don't fool yourself -- this is now as deadly-serious a Crisis Era as any in the past. ISIS now kills non-Muslims (and the "wrong sorts of") Muslims in northern Iraq today. As with fascists of the last Crisis they show no signs of any willingness to let some geographical line constrain them.
Maybe we don't want war with ISIS. I hardly expect ISIS to bend to our sensibilities on war and peace. Maybe we don't want to fight it on its own turf. To the extent that it can conquer it will compel us to fight on others' turf. Vile as it is and with no cause to sue for peace it may finally compel us to fight it on its own turf as we eventually did on the 'sacred' German soil of the Third Reich.
Islam is not the enemy. Multitudes of Muslims find ISIS a great horror offensive to their sensibilities. Plunder, rape, oppression, and murder are not Islam.
The greatest evil is not now done in those sordid "dens of crime" (or) even in concentration camps and labour camps. In those we see its final result. But it is conceived and ordered... in clean, carpeted, warmed and well-lighted offices, by (those) who do not need to raise their voices. Hence, naturally enough, my symbol for Hell is something like the bureaucracy of a police state or the office of a thoroughly nasty business concern."
― C.S. Lewis, The Screwtape Letters