I have never understood why this argument is used anywhere ever. There are two main flaws that I see.
1. If scientists are correct (and I understand that there's some disagreement on this point), then the Big Bang was actually the inception point of time itself. Therefore, assuming that "come into existence" means "goes from a time of non-existence to a time of existence", then the universe never came into existence: it's like asking what is south of the south pole.
2. What is more likely is that the KCA means something different by "come into existence" than most people think. In which case, we may suppose that the universe had a cause. It may be an interdimensional bubble, or a fluctuation in dimensions unknown to us, or it may be a god, or aliens, or even the aftermath of a "Big Crunch", but there's nothing to favor the god interpretation over any other.
Help me out here, Creationists... what's the point of this argument?
™ Version 4.2