You could be right - maybe nothing needs a "purpose" in this way. In which case, maybe we as a species don't need the concept of a god or gods. Perhaps the idea of supernatural deities is successful merely because they give our lives meaning by placing our puny existences into the context of an eternal schema.
I'm not sure; I think this is what DC is saying. It kind of makes sense to me. I guess its not a very strong argument against the existence of God. Its more specifically a response to people who say: "there has to be something more than just this life, or else whats the point?"
I suppose the obvious objection is that people don't believe for such a mundane reason, and that faith can legitimately be founded on grounds other than the uncomfortable reality of a scared creature facing the finity of its own existence. Personally though, worry about death -- the ultimate unknown -- seems to be something very fundamental to our outlook. The sheer amount of faiths that feature some kind of an afterlife seem to me at least to point to gods as merely a comforting product of epic wishful thinking.
Does that make sense?