Sin does have it's consequences, whether the person doing it is a Christian or not, for sure. I just don't think a non-Christian is bothered by their sin the way a Christian is. Many non-Christians will deny there is even such a thing as "sin", though I believe they really know there is and they are just rationalizing it away to excuse their behavior. Once a non-Christian begins to show remorse over their sin they are now at the threshold of repentance and even being born again, such that they are no longer a non-Christian.