And the argument is deceptive, unless you think that it is valid to equate improbability of to Gods existence with the the improbability of God having come about by chance (something virtually no one even believes).
Of course it's valid. If god exists then he must have "come about" somehow. As I have already stated, the idea of his having always existed is an argument with no evidence. If he did indeed "come about", then he was either created by another god, which is not an idea many believers seem to support, or he came about by chance. There is nothing deceptive about that equation. However, since you seem hung up on the fact that he didn't argue the point against the "god has always existed" idea, I'll do it for him, as per my first post: "No he hasn't". There. Done.