There is no progress in blaming others, but I refuse to feel bad for the narcissist. It is possible, even likely, that he suffered trauma in his childhood, but that does not make his actions acceptable.
Maybe, when he was still a young child, I could feel some empathy towards him, but the narcissist I know is a grown man who stands almost a foot taller than me and outweighs me by over one hundred pounds. His physical stature is intimidating to me, and I shudder to think of the perception my children had of him when they were young.
Regardless of his size advantage, he held nothing back while raging and thundering at us. I may understand part of why he is damaged, but I will not feel sorry for him.