First off, I found this issue to be quite frivolous.
But in a way, the athiests do have a point. I believe in God with no doubt in my mind. But we have to look at the Constitution. As mentioned earlier, it used to go "one nation, indivisible, with liberty and justice for all", but then in 1954 Congress changed the pledge of allegience to "Under God". This act of Congress was unconstitutional because the first amendment says "congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof...", and what Congress did was pass a law that favored a Judeo-Christian belief of "God". And just now the Supreme Court ruled that unconstitutional.
Now people like Alan Keyes (who is an idiot when it comes to this issue), think that it prohibits their free exercise of religion. But the problem is the freedom of religion allows you to exercise YOUR religion. The pledge of allegience requires you to exercise ONE UNIVERSAL religion and that is Judeo-Christian, so if a muslim or a buddhist wanted to say the pledge of alliegence, they wouldn't be excersing THEIR religion, they would be forced to exercise the UNIVERSAL religion, which is the Judeo-Christian. And that is part of the reason why the Supreme Court ruled against under God.
Now, people are starting to say that money would be unconstitutional or the Constitution wouldnt because it has "God" in it. But the main reason this went to the supreme court is because some people are required to say the pledge of allegience on a daily basis (eg. schools). And the difference between the pledge of allegience and money is, no one forces you to read every single line of wording on money on a daily basis, nor are you required to read aloud "In God We Trust" on a daily basis. Same with the constitution, although every American is encouraged to read the Constitution, the parts where they talk about man and its creator isnt essential to understanding the constitution.
So, as frivolous as it seems, it does make sense. Just think of it this way, if the United States were an Islamic country, and you were christian, would you feel comfortable saying "Under Allah"? I sure wouldnt. And thats why I understand their point. But thats just my opinion and my interpretation of the constitution, im not in law school yet, Im just a high school junior.