"Why are Christians so self-righteous?"
No one denies there are self-righteous Christians, and it's always sad to hear the tales of their misapplications. But let's make no mistake about it -- all forms of self-righteousness, both secular and religious, misunderstand the gospel message. The scandal of the Christian gospel is that you cannot save yourself. Your good moral standing will never get you to heaven.
I think one of the greatest misconceptions about Christianity is that it’s primarily about morality. That’s not to say morality has nothing to do with it, but in historic Christian teaching, morality is a by-product of the gospel. It’s not the point of the gospel. The first point of the gospel is that our morality is sorely lacking.
I love that about the gospel, because it destroys all grounds of self-righteousness. Most of us dislike self-righteous people, for good reason. But the most basic form of self-righteousness is when we say, “I think God will accept me because I'm basically a good person. I don’t need a Savior, because my self is good. My self is right.”
Whenever we think our soul, our self is right and not in need of rescue, that is by definition self-righteousness. And that is not Christianity. Let me quote directly from the source, the best place to go when you’re examining any religion:
16 yet we know that a person is not justified by works of the law but through faith in Jesus Christ, so we also have believed in Christ Jesus, in order to be justified by faith in Christ and not by works of the law, because by works of the law no one will be justified.
That's simply a blanket indictment against all forms of self-righteousness, which is good news for everyone who hates self-righteousness.
Well, unless you're depending upon your own righteousness to commend you to God. Then you have a problem.
That’s why the gospel has continued to be good news to the morally bankrupt, but not the self-sufficient.
Now, this is something even the Christian needs to remind himself of from day to day, because if you're like most of us who are following Christ, you're going to trip over yourself during the day and others are going to notice. Some might even point it out to you. When they do, your first response will probably be to defend yourself. Don't defend yourself, because that's what God has done for you in Christ. "Who can bring any charge against those whom God has chosen? Christ is the One who died."
Jesus and Jesus alone is the One who has made you right with God. Not you.
So, don't defend yourself. Just admit to the person who noticed that she's right about you not being right.
Then point her to Jesus, too.
Don't defend yourself. Look to Jesus.