Generally a harmless bunch - the link from Georgiansilver above is a complete load of lunatic paranoid bunkum, by the way - and greatly into good works in the very dullest, Round Table and Rotarian sense.
Surely you'd have more fun playing music of an evening rather than trotting along to a mutual back-scratching session with a bunch of lower middle-class white men.
I've been asked a few times, but would rather go to the pub with friends, play music, shoot the breeze or whatever. But for those that have trouble getting a social life together and want some ready-made friends, maybe masonry's the answer.
If it is the answer, it must have been a very dull question, though!