That's what sacrifices were made for in the first place. The fear of an angry god that might kill them if they do not give him something. The word for it is oppression. That's what the gods and religion have always been and will always be, no matter how much they try to stick with science to gain some new credentials.
I'm guessing the OP is referring to Christianity? If so, Christianity does not fit the above quote. Christianity is God sending himself as Jesus to be a sacrifice that humans could never make since they are themselves sinful. As far as rules about how Christians live and what they do or don't do, that's more of a result of having been changed by God, not an attempt to earn God's favor since it can't be earned.
As for proving God's existence, that's probably not the best question since even tangible things from recent history are debated, such as if we landed on the moon or not. You can probably think of more examples. The point is that if even tangible things from recent history are quibbled over, then how much more difficult is the question of God?
This must be the most controversial thread on here so I had to throw in my .02.