This was said in his endorsement of Obama in 2008:
I'm also troubled by, not what Senator McCain says, but what members of the party say. And it is permitted to be said such things as, "Well, you know that Mr. Obama is a Muslim." Well, the correct answer is, he is not a Muslim, he's a Christian. He's always been a Christian. But the really right answer is, what if he is? Is there something wrong with being a Muslim in this country? The answer's no, that's not America. Is there something wrong with some seven-year-old Muslim-American kid believing that he or she could be president? Yet, I have heard senior members of my own party drop the suggestion, "He's a Muslim and he might be associated terrorists." This is not the way we should be doing it in America.
I feel strongly about this particular point because of a picture I saw in a magazine. It was a photo essay about troops who are serving in Iraq and Afghanistan. And one picture at the tail end of this photo essay was of a mother in Arlington Cemetery, and she had her head on the headstone of her son's grave. And as the picture focused in, you could see the writing on the headstone. And it gave his awards--Purple Heart, Bronze Star--showed that he died in Iraq, gave his date of birth, date of death. He was 20 years old. And then, at the very top of the headstone, it didn't have a Christian cross, it didn't have the Star of David, it had crescent and a star of the Islamic faith. And his name was Kareem Rashad Sultan Khan, and he was an American. He was born in New Jersey. He was 14 years old at the time of 9/11, and he waited until he can go serve his country, and he gave his life. Now, we have got to stop polarizing ourself in this way. And John McCain is as nondiscriminatory as anyone I know. But I'm troubled about the fact that, within the party, we have these kinds of expressions.
He was referring to this image: http://www.newyorker.com/images/2008/09/29/p465/080929_slideshowplaton16_p465.jpg