These are the people who put make-up on their image too thick in spots — right where the blemishes in their character are. Since it's all about their image, as Hamlet's mother said, they view sin as some kind of taint instead of as moral illness, or spiritual dis-ease. This is what gives them the notion that it can be "washed away" or smeared off. No wonder that, to get rid of it, they project instead of repent.
So, narcissists are by no means alone in accusing others so as to project their own flaws off onto a scapegoat. It's just that they invest so much energy in doing it. They are fixated on their image to the point that it is uppermost in their mind 100% of the time. It's impossible to overemphasize that.
In contrast, normal people project only when on the defensive. And then they're likely to shake themselves off on whoever happens to be near at the moment. So, their aim is poor, and sometimes they project a flaw off onto someone who actually has it. But a narcissist's aim is impeccable. For example, whom does he call a liar? The most honest person around. Who does he say is dangerous? The savior of the group. Every single time. His talent for farce is so great that you could mistake him for astute.
Also, normal people have normal, human and loving relationships. So they don't smear themselves off on just anyone. They wouldn't dream of harming those near and dear. And they stick to slander (which has at least some degree of truth in it), rarely engaging in calumny (lies). When they do calumniate someone, he or she is an enemy. Even then they don't go hog-wild and calumniate someone so badly and so widely as to destroy them and ruin their lives.
Not so with the narcissist. He is a mental child with no sense of measure or moderation. So, he is more dangerous with his mouth than an angry five-year-old is with an AK-47. He will say anything — ANYTHING — about you as lightly as one would brush a crumb from his sleeve. He loves only himself. He has no normal human relationships. He relates to people as objects. So he will smear himself off on his own children as thoughtlessly as we smear ourselves off on a towel.
In fact, he is most likely to smear off on someone he owes gratitude, because needing help damages his image. So he repays help as though it were an insult. He must devalue it by devaluing the giver of it, as if such a contemptible person is incapable of really helping someone as grand as he.
Since he is a mental little child, the only reign on a narcissist's behavior is what he feels he can get away with. So, the more he gets away with, the more repressed guilt he has to purge himself of.
It's a vicious cycle that he plays the hampster in all his life.