Bad analogy. Jesus did not say that the woman was not guilty of adultery. He merely exercised His mercy and asked anyone there who was without sin to cast the first stone. His mercy trumped His justice, in a way. So it might be with each of us, when we transgress His commandments. But we should not presume on His mercy! He called the woman's adultery a "sin," just as he called the actions in Matthew 5:27 a "sin." As I said in an earlier post, I readily concede that there are gradations to the various "sins" we can commit. Neither direct adultery nor lustful thoughts would be as serious a sin as mass-murder, I suppose. But that certainly doesn't excuse them as inconsequential! Perhaps "looking a someone with lustful thoughts isn't "as bad" as direct, physical adultery, either, but that hardly excuses! It is still sin; Jesus says so directly. As such, it needs to be eradicated. One at least needs to try. Sure, God might take habituation, addiction, etc. into consideration when He judges us. But we don't have a clue to what extent He might do so, if He actually does at all. We only suppose He does to the extent that He judges our "free" actions, and acting under spiritual compulsion of addiction is not really engaging in "free acts." But it is sheer folly to barge on ahead with our objectively sinful acts on this basis! What about the obligation to confront our concupiscent impulses through cooperation with God's grace, as St. Paul more than suggests is necessary in 2 Corinthians 12:9?
We are not mere animals. We are charged to control the baser things our fallen and wounded nature finds attractive. Our life is a probationary period in which our eternal destiny is determined to the extent we succeed in self-mastery under God's grace. We all fall short of that to some extent over the course of our lives. But our victory is in the battle. If we don't even try, how much can we presume God "excuses"? If everything is "excused" as beyond our strength, how can we make sense of not only 2 Corinthians 12:9, but also 1 Corinthians 10:13, where we are promised that God will not allow us to be tempted beyond our strength? It is one thing to fight and occasionally fall short of the ideal through innate weakness, while subsequently repentant; it is another thing to simply not bother to fight at all.
For non-Christians, especially those who are non-Christians by choice, perhaps this whole business is just nonsense. If Christianity is based in Truth, however, that mindset is the real nonsense, for its implications are eternal. But, again, the author of the article which is the basis for this thread is not addressing them. He is talking to, and about, people striving to be better and more consistent Christians. If you want to snicker, go ahead. But this is the Religion Forum, so please consider that many here will have a less materialistic approach to this issue, and might find the author's POV constructive.