“Why believe in a god? Just be good for goodness’ sake.” That’s the tag line of a new ad campaign set to launch next week on Washington, D.C., buses. The advertisement, which is sponsored by the American Humanist Association, is similar to one started in London last month.

According to spokesman Fred Edwords, the group decided the holiday season was a good time to run the ad because “there are an awful lot of agnostics, atheists and other types of non-theists who feel a little alone during the holidays because of its association with traditional religion.”

But American Family Association President Tim Wildmon is calling the ad “stupid”: “How do we define ‘good’ if we don’t believe in God? God in his word, the Bible, tells us what’s good and bad and right and wrong. If we are each ourselves defining what’s good, it’s going to be a crazy world.”