Why couldn’t you just kill yourself or let it go?

Sean Archer: This is between you and me. Leave them out of it.
Castor Troy: No. Sean. “You” should have left them out of it. Your son was an accident. I wanted to kill you. But, you took it so personally. Why couldn’t you blame yourself or let it go?
Castor Troy: Why couldn’t you just kill yourself or let it go?
Sean Archer: No father could.
Castor Troy: No brother could either.
Tasha: Neither could a sister.