I think that Dawkins and his peeps were foolish to take out those bus ads. It makes them look unserious, because they draw exactly the wrong conclusion from the fact that there “probably is no god.” Roger Scruton writes in the American Spectator about the contrast between this new humanism and the old.
The British Humanist Association is currently running a campaign against religious faith. It has bought advertising space on our city buses, which now patrol the streets declaring that “There probably is no God; so stop worrying and enjoy life.” My parents would have been appalled at such a declaration. From a true premise, they would have said, it derives a false and pernicious conclusion. Had they wished to announce their beliefs—and it was part of their humanism to think that you don’t announce your beliefs but live them—they would have expressed them thus: “There probably is no God; so start worrying, and remember that self-discipline is up to you.”
and
Like so many modern ideologies, the new humanism seeks to define itself through what it is against rather than what it is for. It is for nothing, or at any rate for nothing in particular. Ever since the Enlightenment there has been a tendency to adopt this negative approach to the human condition, rather than to live out the exacting demands of the Enlightenment morality, which tells us to take responsibility for ourselves and to cease our snivelling.
If Dawkins wants to win converts he needs to offer something positive, not just be against something.