You Can't Tell A Book By Its Cover

Some Dutch atheists took a Christian bible and changed the cover to make it look like the Muslim Koran.

Then they highlighted various cruel, nasty, horrible texts and read them to the people they were interviewing and all agreed that the texts were cruel, nasty, and horrible. Certainly not the sort of thing you'd expect to find in a holy book. At the same time, however, most of them weren't surprised to find the Muslims believing such rubbish.

Then the atheists took off the false cover and revealed that all the cruel, nasty and horrible texts came from the Christian bible! Every bad thing the interviewees had just said about Muslims now had to be taken back and re-applied to their Christian friends and relations.