OK, let me get this straight...You're offended by something...that doesn't go out of it's way to offend anyone who isn't of Christian faith? FFS, if it bothers you that much, don't watch the show.
I'm an atheist, and I don't care. I preach religious equality as much as anyone, but I'm sure as hell not offended by this. Honestly, it's like you're looking for a reason to be offended. Hell, I am an Atheist and that song doesn't offend me, in fact, I enjoy the song because it has a nice sound, it's promoting peace and harmony, AND IT IS NOT SAYING ANYTHING BAD ABOUT ME.
If they sung a song about Buddhism, I would not be offended, if they sung a song about Judaism I would not be offended, if they sung a song about the Greek Gods I would not be offended. And you sure as hell wouldn't be offended if they sung a song about your respective religion. And you're calling American Idol close minded?
They haven't done ANYTHING offensive at all. They did not say anything but goodwill towards man. And you're calling it offensive.