I understand your point. However, because I believe that any kind of sexual activity outside of marriage is wrong, and being a single guy, this presents a problem for me. And again, I cannot stress enough, I am not saying that it is a sin just to wear diapers. That would be an incredibly foolish and ignorant thing to say.
In regards to your quote, it is true. But forgiveness is something that shouldn't be taken for granted or taken advantage of. When someone you love forgives you for something, typically you don't turn around and do it again.
Please understand, this is my struggle. I am not condemning anyone, and I don't expect anyone in here to live to the standards that I do, especially if they don't believe in them.