In the article. the author says: " de Botton has done a marvellous job of summing up what it is to be a nice human being."

So I wonder why 'atheist' and 'non-believer' have to be equated and named in order to just provide a nice list of virtues?

I never wrote out a list like that, but I have always tried to act in such a way that such a list might describe me. Now, if 'believers' would all do the same, those apocryphal stone tablets might not be needed.