Perhaps the greatest problem in dealing with the concept of "sin" is humanity's inability to deal with personal responsibility.
For instance, even though the major message of the New Testament is about personal responsibility, love, grace, etc., the church as a whole would prefer to punish people for not following a list of rules. It's much easier to blame the whole thing on God, come up with rules which must not be broken (and which are easy to point out people breaking) and then feel righteous.
Sin, in it's true nature, is short-sighted, selfish thinking.
You push somebody. You lie to somebody. You cheat on somebody. You steal from somebody. It's hurtful, it's "let's be happy right now", it's selfish.
Sin divides us from each other, and breaks apart the connections and trust possible between humans. Look how many of us, by the time we're "grown up", are nigh incapable of true trust, and expect to be betrayed in work, relationships, etc. We think that cheating is normal, and that it's every person for themselves.
Even more insidious than actual actions though (many of us can probably say that we don't go around hurting people, or lying, etc.) is short term thinking. This breaks down into two factors:
- "The Road to Hell is Paved with Good Intentions". This isn't just well meaning efforts that screw people over. This includes being fuck buddies and various other like efforts, which are fun in the meantime, but almost always wind up either A. Breaking up the friendship when an emotional attatchment is formed, or B. continue to be fun, but dull us emotionally in our ability to find intimacy with others through sex, something which has become a generic activity for the pure expenditure of stress and horniness.
- Thoughts in general. Oops, to qualify: Dwelling on how you dislike somebody. Or how much you'd like to fuck someone. Or on how you'd like to hurt/steal/gossip/ what have you. Seems like no particular big deal, but what's it doing inside your head? You may not act on it now, but it's slowly, bit by bit, making it easier for you to think about doing it next time. And the next. And the next. You're forming habits. Scarring away sensitivities.
Sin isn't about "I'm God, and here's this list of rules you need to obey to please me, because I'm bad like that".
It's about "I'm God, and I created you a certain way, with a certain emotional wiring, and when you do things on a steady basis, you screw that wiring up, you damange yourself and your ability to operate in a healthy way."
But you won't hear that from the church. It's too gray, too middle of the line. Not enforceable, not so easy to point fingers with.
Even though, if God hates anything more than anything else, it's active divisiveness. Anything that drives people away from each other is a bad thing to Him. Interesting.