Some people cannot deal with the truth.
If you've ever actually dealt with a domestic abuser, you've probably noticed something downright infuriating about them. Though they can see the damage they do and the glares they're getting, they never really see themselves as the bad guy. No matter how much evidence you throw at them, the sad fact is that many abusers will argue that "it was deserved" or some other ridiculous justification until the day they die.
Having been there, I've always wondered how it's possible that an abusive, horrible human being can't see themselves for what they really are. As one would expect, there's actually a psychological reason for that and, believe it or not, it's something that's latent in everyone.
The easiest way to say it is that no one wants to think of themselves as a bad person. In our minds, we are the protagonist in the big story that is life. With many people out there, the idea that we could possibly be bad people or do bad things is something that just doesn't jive in our minds. This is why we might justify our wrongdoings to others who judge us.
Narcissists and others like them desire to see themselves as good people. They need to see themselves as a victim and as a good person because their current self-image can't handle otherwise.
Moreover, admitting that they did wrong is something they see as a failure or giving up control, and that's something abusers will never do. What we see when abusers refuse to see themselves as bad people is a clash between a personality disorder, a need for control, and the cycle of abuse.
So, what happens to people who need to protect their fragile minds from the horrible truth of who they are? They get delusional or they pretend to get delusional in hopes they can get you to believe that you're in the wrong, which will let them feel at peace with the sins they committed. They start making up their own world and start doing mental gymnastics to try to reclaim the very "goodness" they flushed down the toilet by treating people badly.
Think about it for a moment. If you've spoken to an abuser, you've probably heard him make pretty wild excuses for his behavior. You may have heard him minimize what he did, make up things that you did, or even just tell you that "you deserved it" because you did something he didn't like.
All of these things are things someone says when they want to keep thinking of themselves as a good person.
This is why it's so hard to get them to admit wrongdoing, even when there's proof. If there's visible damage and serious evidence, they may admit they were wrong for a short period of time... only to revert back to it being "your fault" in some way when the evidence disappears. In some cases, the person might be so far gone that they'll deny evidence to the contrary even if it's shown right in front of their face.
To further prove the point, think about how abusers work. They often threaten their victims into silence or do "damage control" if their victim decides to speak out. They also do smear campaigns to ruin a victim's reputation if a breakup ensues.
It's not just a coincidence that politicians do the same when they are caught doing something terrible by a rival. It's because it's a reputation saver and helps them ensure others will reassure them they're in the right.
This is why you should never hope an abuser will see his wrongs for what they are in the long-term. They know what they're doing is wrong but the fact is that they don't care enough or don't allow themselves to process what they did in a way that will make them change.
This is also why you shouldn't try to change them or force them to see what they did. If you're with an abuser, your best bet is to leave and disengage with them the moment you notice a warning sign — and it's better to leave late than never.