What you said is that if you are aethist you never feel the need to be decent (i.e. saying you're sorry) because you have no reason to be since in the end no one will judge you. Is that an appropriate assessment or not?
No an atheist living in the United States has to be 'decent'. Where do we get our laws from? Not from people. They were derived from the Ten Commandments. If there's no God, then there's no accountability. Look at China. Look at countries governed with atheism as a state religion.