The last part, I don't understand you at all. To ignore the deleterious effects of reenacting past hurts in the current relationship strikes me as delusional.
Maybe I didn’t understand your post. When I say “I’ve heard this too as an excuse to not become vulnerable and to maintain walls…. Just another deflection” I am thinking about people who use the excuse “If you beat the crap out of me because your father beat you, it's not about me, but I'm still just as bloody” as a reason to not open up. To me they are acknowledging the other person’s issues but still use that person's aggressiveness as an excuse to stay behind their defenses (which doesn't mean they should expose themselves to physical harm). That’s all I was getting at.