On what grounds? Apparently they committee felt that:
"...the language of the ads was specific enough to attract religious debate and polarize members of the community."
Let's simply ignore the cultural debate about the merits of religion in public life. Politically, this just reveals the arbitrary nature of what is allowed and disallowed whenever we have "public" institutions and boards claiming to represent all of "society". Inevitably, they end up discriminating against certain minority points of view, views which may not be able to otherwise be heard due to the monopolistic nature of many of these public services. If it were easier for private companies and institutions to emerge, I'd venture to say that there would be ample opportunities for nearly all viewpoints to be heard - without having to ban certain others.