The author of the letter to the editor started out on a racist rant  with an anti-gun rant included.  

"yet another lone “angry white male” perpetrates a mass slaughter"; " gun after gun after gun up to his room"

GBA countered with the death rates of black males by black males in Chicago even though it is one of the most highly gun-controlled locations in the US.

Genetics wasn't mentioned; cultural disposition wasn't mentioned---except by you.  

That sort of thing is a Margaret Sanger Eugenics argument.  (The Negro Project")

And you have chosen to ignore that almost always those ' innocents in those neighborhoods...grieving mothers, father, brothers, sister' are black themselves.

If those in the neighborhood won't testify because of fear, or identification with the killers, ("Warn A Brother" T-shirts?) or some other reason, empathy is hard to develop.  

Especially when you see someone come from that kind of background and still succeed.  Cabinet Secretary Ben Carson?