There are two varieties of Athiest:
Variety One, or the True Athiest, is rational, polite, and maintains a "live and let live" philosophy. True Athiests are not perturbed by the outward displays of other peoples faiths, such as nativities, menorahs, or whatever. They simply don't care. They are more than capable of joining faith aligned organizations such as the Boy Scouts, usually doing so as ostensible Taoists or under the ever so useful umbrella of Unitarianism. They usually make excellent neighbors (and very good Scouts).
Variety Two, is a much noiser breed, and therefore easier to spot and more often mistaken as the genuine article. This is often called an Athiest, though it is really a False Athiest or, more technically, another term that starts with 'A' (and rhymes with 'Bass Hole'). This type has turned non-belief into a false religion in itself. It also never misses an opportunity to proselytize its belief in lack of belief, and always work hard to enforce its own non-belief on others. This variety finds it very difficult to become Boy Scouts etc., because the Boy Scouts themselves are smart enough to know trouble when they see it. These almost never make good neighbors.
Which sort do you suspect Mr. Flew is?
Best regards...