People often question the existence of good and evil. I recently read a question where someone was asking about the existence of good and evil. They said, “What about a person that was brainwashed to murder since they were a kid?” Here was my reply:
That is true that many traits we possess are either socially influenced or genetically influenced. However, good and bad do still exist, simply because it is a matter of choice we can all make.
For example: Regardless of how a person is raised or genetically inclined, they still have a choice of whether to do bad or good in a situation. There are lots of people brought up in a loving home, and have seemingly fine genetics, however, they may make a conscious decision to cheat on a spouse, or lie, or, etc.
I can be brought up to eat pizza everday, and maybe I have a genetic pre-disposition to eat pizza, but do I not make a choice of sticking pizza in my mouth? Can’t I also eat other foods? See, it is all a matter of choice. God is more concerned with our choices in life (ie choosing to follow commands or not).
We are not held accountable for that which we have no control over (like in your example of someone being mentally abused and brainwashed their whole life). We are held accountable for that which we consciously know is wrong, yet we proceed to do it anyways.
There is a verse in the bible that touches on this (off the top of my head), they are asking Jesus something about it. And he said something to the effect that, “One person knew their masters orders, but chose not to follow. That person will receive a severe beating. Yet there was another that didn’t know his masters orders, and didn’t follow. He will not receive such a bad beating.”
So I think God fairly judges us based on our knowledge, and what we choose when we know both wrong and good.