With regards to God in particular: God exists in a lot of peoples' heads. He's a massively parallel distributed cognitive algorithm that millions of people use and model. . . . In that sense, and it is an important sense, God is very real. More than that, all memes (memetic algorithms) are real.

But that's not the sense that theists mean when they say "God is real", and it's definitely not the sense that atheists mean when they say "God isn't real". When someone says "God isn't real", it's not like they're saying that God is not a meme that exists in anybody's mind — a person needs to have their own mental copy of the God algorithm, and the understanding that millions of people share it, in order to even bother being an atheist. It's pretty clear that they mean that the God algorithm isn't a model of any actual agent that created the universe or acts on it independently of the humans modeling him.

So I'd disagree with "In that sense, and it is an important sense, God is very real." Clearly in that sense God is real, but it seems like a profoundly unimportant sense to me, particularly because I don't think anyone actually uses "real" that way. It seems like a type error; a god is an extremely different sort of thing than the idea of a god.