“ISIS is to Islam what the KKK is to Christianity.”
This analogy is not really effective because a large percentage of people in this secular world don’t believe in Christianity and even think of Christianity and certainly the Bible as atavistic and inhumane. So the analogy will sound flat in those ears. Try this analogy instead.
ISIS is to Islam what the Democratic People’s Republic of North Korea is to democratic republics.
Or if you’re feeling extra spicy:
ISIS is to Islam what Operation Iraqi Freedom is to freedom.
ISIS is to Islam what the US Department of Defense is to national defense.