If you had 100% solid proof that the christian god exists..

[quatona]

Atheists believe it is wrong to steal, murder, etc...just as the religious do...they just believe it for different reasons. The religious believe it's because God says those things are wrong... whereas most often atheists believe it's wrong on humanistic terms (those actions are harmful to society...etc)

I´m not sure this is an entirely accurate distinction. In my observation most Christians believe it for utilitarian reasons, too. At some point their arguments usually become entirely utilitarian (e.g. "...but then [insert person who has committed severe crimes] would not be wrong/evil").
So god appears to be not so much the reason, but more the tool in their line of reasoning.