The case that the tumor had much to do with Whitman's behavior was never considered definitive. Meanwhile, his ferociously messed-up childhood is beyond question. His father was extremely, notoriously angry, demanding, and physically violent, both to him and his mother. His mother left his father after the kids were grown to live alone and work in a store, just to get away from the beatings. Charles became violent to his own wife after they married at 20. He was initially a high achiever in academics and sports, but less so when he was sent to college on a GI scholarship. He drank and gambled and had fits of rage. He was court-martialed by the Marines for loan-sharking other Marines, threatening them, and keeping a private firearm in his room.
The father apparently had no tumor. If the son acted like him after growing up around him and being beaten regularly, the tumor COULD have been an extra factor, but as an explanation, it seems unnecessary. Personality traits and some behavior tendencies are heritable, and random beating and cruelty in childhood are known to leave the victim with a reservoir of rage that can inspire him to victimize others.
I don’t believe that tumors are inheritable as you seem to do.