While acknowledging the factual correctness of atheism, he doesn't want people to respond to their newfound atheism by actually changing any of their behavior surrounding religious institutions and rituals.

Alain de Botton is quite possibly correct that "religious institutions and rituals" supporting an ethical system could exist without involving any theistic cosmology or similar doctrines. Confucian 'religion' is a case in point. Yes, Confucianism evolved from Chinese ancient religion, but it developed independently over many centuries as a non-theistic system. The same process could occur with modern Western morality, which historically evolved from Protestant millennialist Christianity.