as far as i can tell, it's not good to hurt other people. so yeah stealing is "wrong" if it hurts someone else.
Well, that's one way I would define "sin". So just because you don't believe in something doesn't mean it isn't what it is. It's just your way to justify not "believing" in God.
That's the key thing here. Because organisms still have problems, they strive to fix them and prolong their existence. That's where sin comes. Because there's still wrongdoing, we try to minimize the amount of it that's going on, and that's why we keep ourselves alive. It gives us meaning in life.
i fixed all of my problems and it's super boring now. don't do that.
really. I had lots of personal problems with my self as a teen and now that I've fixed them enough to be satisfyed with myself it's all sort of "meh I can do that but what does it do to me?"