Because it repeats a rather pretentious and disgusting truism - the idea that everyone 'believes' when push comes to shove.
The saying "there are no atheists in foxholes" (and a similar statement, just as bad, "there are no atheists on birthing beds"), is a common fallacy. Essentially, that even someone who states that they do not believe in God will 'demonstrate' that they believe by praying in a foxhole when under fire.
Except that it's wrong. Even though some atheists revert to old beliefs when under stress, many do not, and even if they did, it is not particularly representative of what they believe now. It's no different than, say, a Jew who converts to Hinduism still calling on his old beliefs when under stress.