As an atheist myself I'm actually torn about the ads. On the one hand I don't see anything wrong with the ads in and of themselves. I mean almost every single day I see a religious ad. The part that tears me is why they put them out around Christmas. It seems I only ever see the atheist ones come out around Christmas and of course all it is going to do is make believers mad and thus make atheists look even worse than they already do. If such a thing is possible.
Anyway, it's only an ad. If it doesn't apply to you just ignore it and enjoy the holiday season.