Well that is very optimistic. I'd be impressed if we saw Christians be exceptionally moral and decent people that rises above the norm. But to be honest, we don't. In fact we have a of examples of Christians being highly immoral and even criminal. For example the Confederate South were Baptists, yet they tried to justify slavery through the Bible. The German citizens of the late 30's and the early 40's who cooperated in the extermination of the Jews were largely Catholic and Lutheran.Because we do know who they are, at least some, the evidence is their changed life and ours. It’s not an empty promise that God gives believers. He gives the Holy Spirit, power to live a godly life free from the power that sin and death has over people. So in your example God’s grace would enable believers the ability to shoot 18 hole in ones on the golf course.
If these people go about their lives assuming they have special favors from God while they have beliefs that are against basic human decency, something has failed with the theology.