Well since the most common argument that theists like to use tends to be the cosmological one, I would say no, as the deistic god implied by the cosmological argument is not "immature" in the "bearded man sitting on a cloud" sort of way.

The problem is, theists are so slippery when pressed into defining their own god, that often we have to guess or make assumptions about it. I'm not sure if there are two theists in the world who agree what god his and what his nature is.

Actually, what I think you'll find is that people often become atheists after having studied religion without a confirmation bias. I my self was only a Christian because my school had drilled it into me, but when I became interested in religion and spirituality, when I started reading up on the history of religion, when I first opened up the bible and read it, that, was why I became an atheist.

Who was it that said, "the best way to become an atheist is to read the bible".

Do you mean right now? Because right now we can't test to see if there's anything outside our universe. We can't test the conditions before the big bang, because singularities don't follow familiar laws of physics. That is why it is useless to make claims about the supernatural, as they cannot be tested or falsified.

We can test, or could test, everything within our own universe. I am not the smartest person in the world, and if you could give me an example of something we couldn't test, I'd be happy to accept it, providing you're right.

Long story short, if we can't test something, it is not reasonable to assume it's existence or that it works, because there's no way to find out.

If you are going to make use of reason you have to believe it will be worthwhile.

We know reason is worthwhile, it can be shown to work.

I have faith that the sun wont explode tomorrow.

You don't need faith for that. We have evidence the sun won't explode tomorrow. We have predicted the path of the sun through our galaxy, we have seen it rise everyday for thousands of years, we are constantly monitoring the chemical processes going on inside it, we have worked out the elements that make up the sun. We have observed how other stars die.

From all of this knowledge, we can predict with far more accuracy the likelihood of the sun exploding tomorrow than by merely guessing, as theists do when they guess that a god must have created the universe.

You need faith if you admit you are likely missing seriously important evidence.

Like I just said, you only need faith when you don't have evidence. If there is enough evidence, a prediction/hypothesis will stand up, if there is serious evidence missing, then we can't be sure and we have to wait until better evidence appears. A good example of this would be string theory. There is some evidence for it, and it seems to make sense in some areas, but there is too much missing for it to be considered the correct explanation yet. Physicists are still working on it. They don't sit there and go, "well, we are missing very large pieces of evidence that X is true, shall we just accept it as scientific fact anyway?".

Tests are still more reliable than guesses. That's what tests are for.

Ahhh, presuppositional apologetics, the Christians finally admitting they've got nothing left to argue with.

Well, I'll tell you why reason is different to faith. You can test reason. Reason is reliable, repeatable, reproducible, and accurate. Faith is admitting something can't be tested but believing it anyway.

You don't have to have faith in reason. Reasoning is demonstrably accurate, as it uses the laws of logic inherent in the structure of the universe.

You only need faith in things you have no evidence for.