Was this somebody you know, or a random stranger?

Random stranger. (Sorry, I meant to make that clearer than I did. Most common writing error in the world is to forget that the audience doesn't already know everything you know...)

I think he is trying to do the internet equivalent of door-to-door evangelism...rather than a typical sample of what he might say to people in general I think he is doing it as his job or what have you. Like, "I see you have not yet removed a clubcard from your wallet. Do you have one? We have these leaflets, all you have to fill in is your bank account details, address, mother's maiden name, IP address and political alleigance..."

Since several people have speculated as to his motives: he turned out to be an atheist himself, and apart from very tentatively wondering if the cause of general rationalism might be advanced by people like me being willing to declare atheism publicly, he mostly just seemed to want to chat about it.

(I'm posting this same response at about five places in the comments to this post. Suddenly I wish LJ had a means of re-merging lots of branches of a threaded discussion in some way...)