Atheists are right-- there is no scientific proof of God.
But they forget that Theology is outside of the realm of Science. Science doesn't tell us what is moral, or ethical, or anything else that may happen to be outside the realm of what science is capable of telling us.
Science is a philosophy of skepticism and empirical evidence, and as such has no ability to explore metaphysical questions, which have nothing to do with skepticism or empirical evidence, and everything to do with subjective experience.
They are simply two different, separate, and exclusive realms of knowledge and thought.
If this is true - and it's not - then why do religious claims about ethics and morality always appeal to scientific claims for justification? For example, bodily resurrection, emaculate conception, the whole world being drowned in flood waters, the Earth being 5,000 years old, etc., etc.
The number of atheists who get pissed about people making ethical claims not grounded in demonstrably false claims about the physical world is, I'm guessing, pretty small.