the Christian and Muslim leaders saying, "We don't mind, it'll get people thinking about religion and God and is therefore good press!"

Yes - apparently the National Secular Society is miffed that they've taken it that way (you can't win with some people...)

Honestly, though... the idea that there is no overarching purpose to existence and no afterlife is actually one of the more depressing ideas I know of.

Particularly the lack of purpose, I think.