Besides the fact that it’s a rebellion against the will of God and contrary to covenants that disciples of Christ have made, the problem with sin is that it promotes selfishness. In the way that it focuses our attention on our own desires and on gratifying them, magnifying their importance in our lives beyond a proper proportion, sin drives us to become that much more narcissistic. Sin is self-involvement personified. Sin and humility cannot coexist, nor can sin and charity.
This is especially bad because we have all been called to develop precisely those virtues–humility and charity. A large part of our existence is to be spent in serving others. We can’t do that if we’re spending time on things that bring us temporary, physical satisfaction, instead of making sacrifices for the good of others. We can’t think about filling our own increasing appetites at the same time that we’re thinking about the needs of widows and orphans.
Which is another problem with sin: it’s a waste of time and a waste of energy. Oh, yeah, and we can’t forget that God said not to do it–that’s still the big one. So by my count, the score stands at: Righteousness 5, Sin 0.