No, I don't believe that sin necessarily leads to "damage done". The bible commands, for example, that
one ought not to mix cotton and linen. Does this lead to "damage done"? Obviously not. The same with eating shellfish, resting on a day other than the Sabbath, and a litany of other sins.
Nor do I believe that repentance is required or need for atonement. I'm an atheist, so sins against God are, in my opinion, hurting the feelings of a non-existent being. Since I don't believe in Hell, I clearly don't believe that atonement is necessary to avoid it. And also I do believe that I can live life how I see fit. What else can one do... live life in a way that they don't see fit? What is the benefit in that?
I believe in things with evidence, and you're still lacking it. Instead of asking rhetorical questions, perhaps you ought to "Google" what others have said about the reasons for Christian beliefs about sexual immorality so you can come back with reasoning.