I think a lot of people (non-christian) get offended and dislike Christians because they believe that all we do is go around telling people what is right or wrong, judging, and I think a lot of us do.
What we Christians need to remind ourselves about is the fact that the bible talks about sin, not right and wrong, and sin has nothing to do with what is right or wrong. Right and wrong can vary. They depend a lot on circumstance. For example, the vast majority of people would say that killing a person is wrong, but if you say to them 'What if someone came into your house and was about to kill you, would you kill them if you had the chance?' and they would say of course!
For right and wrong there is a scale. You can be partially wrong or right. It could be wrong to steal today and perfectly fine to steal tomorrow; in other words right and wrong are relative.
Sin is a completely different issue. It isn't about right or wrong, it has no scale. Sin either is or isn't. You can either sin or not sin. And this is because isn't about us or our circumstance or anything else, sin is about God Himself.
With sin, we only have two choices; God's standard or sin, and God's standard cannot change, it is a fixed point, which can be likened to the bar on the High Jump in athletics. You either clear the bar or you don't.
Understand then, that anything even a little less than God's standard is NOT God's standard, and therefore it is sin.
And this is exactly why we need Jesus. No amount of doing the right thing can bring you to God's standard, because it is not the doing of the right thing that takes you up to God's standard, it is BEING God's standard, being inherently righteous, being right.
Think this way about it, if someone has even one percent out of one hundred wrong, they can NEVER attain to God's standard, because 99% percent pure is not 100% pure, and you can add as much pure as you want, but that impurity remains.
So because only God Himself is inherently pure, without even a hint of impurity, He sacrificed Himself, sending us His 100% purity in exchange for our impurities, so that in this way we could attain the otherwise unattainable purity that is required to be with Him.
That is why Jesus was born of a virgin. He had to be. The bible says that from day one we are born with the desire to sin (be dishonest, take what isn't ours, put ourselves first etc.), in other words we are born impure. It's in our genes. In the same way that a drug addicted mother can give birth to a child with an addiction, or a mother with AIDS can give birth to a child with AIDS, sin is a generational defect that no amount of chemistry can do away with. So God sent Jesus into Mary, to be born in human form without the sin defect, so that He could be God's perfect standard in human form, the perfect sacrifice, the perfect exchange.
So Jesus came here perfect. He gave us His inherent righteousness, and took all our impurities away, separating us from them for eternity (should we want Him to) so that we can finally be accepted, having His inherent righteousness, and thus attain to God's standard.
This means that whether we have always done the 'right' thing or 'wrong' thing, God, in Jesus, has given us the key to become inherently right, through and through righteous, which means we are above judgement (I don't mean in a Worldly sense; if you break the law you go to jail end of) meaning that we are now above the scale of right and wrong and we are a part of Him, with Him, in Him, RIGHTEOUS.