First, the atheists' message is self-evidently not 'reasonable', since the majority of people seeing their billboard will not in fact agree with them. So there's a self-imposed limit on how much damage a self-contradictory, smug little message like this can do.
Second, the Catholic League billboard in most contexts wd be so ordinary as to attract no notice -- we all see things like this around all the time. But it's a sad commentary that the League doesn't think God can take care of himself; that the Almighty needs them to rent billboard space. As the article-writer suggested at the end of his piece, there are more Xian uses for that money.