Indeed, the mere fact that God is something people have to 'believe' in is evidence enough. But people always ask about God. No one would jump off a ten story building, claiming God would save them. There are endless rationalizations for this. Thou shalt not put thy God to the test.
People believe in gravity.
You drop a dish, it falls. You drop off a tall building, you splat. It works . Newton, and Einstein, and Darwin, are tested all the time, day in and day out, and scientists dream of having them fail. The scientist who finds where another scientist was wrong is on his way to research grant city, maybe even to Stockholm.