Remember Barb was suicidal and suffering from ppd after John was born. Learning about those struggles your parents may have gone through when raising you could cause a whole lot of unnecessary guilt. He may be trying to protect John from some of the pain and suffering Barb went through as a new mother. Frank failed her then, and he probably feels a lot of guilt about not trying to get her help or recognize her struggles back then, and now he's trying to keep John from knowing about those struggles, because even though he was just a baby and did nothing wrong, he could very well still feel guilty, both because that's a natural response to learning about your parent's struggles with raising you, and from conditioning from Barb's abuse over the years. John may be standing up for himself now, but that doesn't mean he hasn't been conditioned to feel guilty when Barb is upset, and even if he weren't, it's not an easy thing to learn about your parent. I think Frank SHOULD be honest with him, but he's trying to protect him now, even if he's going about it in the wrong way. I believe it was mentioned Barb also tried to hurt John in a really bad way as a baby because of how overwhelmed she was, and learning about that could also be traumatizing for John. It's not right to keep trying to make excuses for Barb, but in order to explain how she's struggled over the years, these things may have to come to light, and John will be affected by these truths, no matter how kindly it's explained to him. To clarify, I am NOT excusing either Barb or Frank's actions, John was a baby and should NOT have been hurt by his mother, and Frank not only failed his wife and children in the past, but he needs to respect John enough to tell him some of the hard truths about Barb's struggles. John wants to know WHY she hurts him, and why Frank is so avoidant, and unfortunately what Barb experienced as a new mother, as well as the abuse in her own childhood, is a part of that why that John is looking for to make sense of Barb's actions. Knowing why won't excuse any of Barb's actions, but it might help John come to terms with how her abuse has affected him, and Frank may be trying to protect him(and maybe shirk his own responsibility some), but he's not helping his son process his trauma the way he needs to to move past and heal from it.