Denial seems to be a pretty negative self destructive thing to do to yourself, it is strange to think that we develop such a self harmful behaviour as a self preservation strategy.
To think that you can do the negative without the negative consequences seems a pretty self destructive approach to life. You can't eat the cake without getting fat and sludge your arteries. But if someone forces you to eat the cake it is better to don't focus on the negative aspects that come out of eating that cake.
It is in fact a self protection strategy, in order to develop denial you have to be trapped in an abusive situation where your natural fight or flight instincts are not enough to lead to a resolution.
Like for example being locked in a gulag or being born in an abusive family, your chances of self defence are non existent in this two situation.
So in order to protect yourself you internalize the abuse, to reduce the amount of external abuse you are going to experience. If you had parents that were very particular about you doing certain things, and if you didn't do some of those stuff they would use violence or manipulation techniques. You would really want to avoid that situation so you would stress yourself a lot and you would internalize what your parents told you when you didn't succeed to meet their request. You do this in order to avoid more external abuse, which actually makes sense as self preservation.
When you internalize the abuse you externalize the responsibility, because you concluded that there is nothing you can do to solve the abuse so you just adapted to it. This might be true at the moment, if you experienced abuse when you were a child there was nothing you could do at the time, but now you are an adult you have option you didn't had when you were a child.
Unfortunately there is a tendency to build bad habits during the helpless period that sometimes follow people for their entire lyfe.
Because there is no way to defend yourself you suppress your anger towards the abusers, you see the purpose of anger when it is express in a healthy way is to create safety. When you suppress there is a huge chance you will use your anger to abuse others. Instead of using it to create safety for yourself and your loved ones, you hold it in and lash at weaker and more vulnerable people than you because it gives you relief.
Sadist find inflicting pain on other innocent people pleasurable not because they have something personal with that innocent person, it is because they have something personal with the original abuser that triggered their anger but never did anything to express it.
This type of sadistic abuse is often justified in society as being necessary to keep society running of course we don't do it because it gives us pleasure. People that are in denial are not very aware to why they do what they do. So this is how this "virus" gets passed from one generation to the next one.
