Taking off from my comment on the topic in the same sex thread:
For me I always associate the word "sin" with religion, and since I'm not all that religious, that word doesn't stick with me the way it does others. I don't use it to describe things I consider bad.
That said, if we're going to bring the idea of sin into the conversation, I think when it comes to serious crimes, a sin may be what led someone to commit the crimes (an adulterous affair leads someone to kill the spouse so they can be together, somebody robs and kills someone for their money, that sort of thing), but to call the serious crimes themselves sinful seems too simplistic, too easily explained away or something, if that makes sense. Things like murder, rape, abuse, those are significantly harder to redeem in any way, if they can be redeemable at all, and I always associate sin with something that you can stop, that you can change, and that you should change because it's harmful to you or other people.
People talk about the seven deadly sins, and I don't think some (or one could argue even all, maybe) of those are bad in and of themselves, it's how people deal with them that matters. Lust in and of itself is not a bad thing, I don't think. We're humans, we have hormones and we're going to find people attractive. It's how we act on the attraction that matters. Pride isn't bad in and of itself, either, again, how we show that pride matters.
Life is just too complicated to say this is always right and this is always wrong and label anything that doesn't fit with your worldview a sin.