Everyone "sins" or "not think things out"....whether its a believer or not. Everything from a deviant thought to acting out, possibly that deviant thought. If ANYBODY says they don't.... they are lying.
Sin is strictly a religious concept. You don't understand that when people say they don't believe in sin they're not saying that nothing is bad. People do bad things and some things are definately right and some things are definately wrong. They don't believe in your religious concept of sin. It's that simple. Although, you will probably refuse to understand.
You guys made up a word. As such, you got to define it. As defined, sure! Everyone sins. But I don't think you would agree that you tropplebleek almost every day. Even if the definition of such is something you would agree you do every day.
it depends on how you define "sin" if you mean doing something wrong, then yes we all sin from time to time. BUT, it you define it as what the word actually is as "as crime against God or his rules" then no, I have never sinned, in order to sin there wold have to be a god and the belief in mythology is not in my nature.