He screamed that he had dealt with it and that is why he's only close to his parents, brother and I.
Your above recollection of what he said struck home with me.
When I think about the effects of shameful feelings on me, one of the most lasting ones is the behavior that seems to want to always draw the line on who knows what. This is a natural human response. Unfortunately, it never seems to leave some part of one's conscious life.
One thing you might do is not be hard on yourself for bringing it up, but consider other ways that you can allow him some space to have the memory without there being unpredictable consequences.
I think in our impatience we want to make things better. Just knowing that there is room to explore needs, even if they are new, scary ones, can help.
Another thing you might look at is the book "Parenting from the Inside Out". As a parent, I have found it helpful in getting some backup to making connections between my own upbringing and the experiences I am having with my children. It is easy to let this go from time to time, but good to be reminded, even when the going gets rough.
Hope for yours (and his) healing,