I'm a Christian, and I think this meme is wrong. Yes, they have killed people. But you don't judge a belief system by its abuses. The Bible says "you shall not murder," but people disobeyed and went on crusades anyway. They were abusing the real intent of Christianity.
I don't know what the Qur'an says, so I can't judge if the killers are actually obeying the intent of Islam.
