Really?
Maybe you are reacting to a certain portion of the post? Yes, the opening sentence. If you are to read the rest of the post, it would seem that it is intended ,by the poster, to be read with that first sentence as an agreed upon assumption. I can't do that any more than I can vote for a political bill with something objectionable tacked onto it.
But I can relate to sin as being something that grieves God and shows some disregard for Him. If not as an adulterous wife, even the example you gave earlier of the prodigal son?
If we deliberately sin, we know it grieves God. We love Him, and if we think about it, we are sorry we did something to so disregard Him. Right?
I know the times when I have really been struck by something I did, right to my heart, it wasn't because I was afraid I was going to hell because of it. It was because I saw how ugly what I had done was in God's sight, and I was so sorry for having grieved Him in that way. Just the understanding of something like that naturally brings repentance, I think ... not that we reason with ourselves that "hey that really was a sin, I am supposed to repent" but that instant, heart-wrenching moment when you see you just stabbed at the heart of someone you love, who loves you, and you can't help but be sorry and never, ever want to do it again.
(In most of this discussion I have been thinking of those minor sins I try to keep a "short list" on ... getting a bit miffed because someone cut me off in traffic, etc. But in this case, I'm thinking of a selfish, deliberate sin that we choose.)