Wrong, it doesn't start out with "there is no supernatural", it starts out with, "the supernatural is not subject to rational investigation".
all I've been trying to say is that since science can never cross that line, to me, it is atheistic.
Science is neither theistic nor atheistic. It has absolutely nothing to say about the existence or non-existence of any deities. Science can examine the specific claims of particular religions and compare them with observed reality however. If the findings of science contradict the beliefs of some religions while supporting others then that is a problem for the religions being contradicted, not for science.
Put it this way. Supposing science had formed the conclusions, solely from examination of the physical evidence, that the universe is 6000 years old and biological kinds were separate creations at around that time, and there was a global flood around 5000 years ago. Would Christians under such circumstances still be declaring that science was atheistic? Somehow I doubt it. Religious people only have a problem with a science when it appears to be contradicting *their* religion. Not when it contradicts everybody else's.
Well, I think I qualify as one of those people but I don't have a problem with science. I just point out it's limitations. Science measures light from galaxies and concludes that that light has been traveling billions of years for it to reach us. I don't have a problem with the fact that science is wrong because it has to be. It has no other recourse.
What it means is that science and scientists are kind of like blind people trying to figure out what things look like. It does get a bit tense when the blind people don't realize they are blind and insist that things look one way when people with sight can see how things really look. Many of these blind people realize they are blind and stick to "well this thing feels, tastes, sounds and smells like such and such but that's all I know".