Having just read this thread I do agree that we are in a 'I blame my childhood' attitude BUT saying that there are some people who have had really terrible parents.
My mother is mentally ill with depression, nervous breakdowns and alcoholism.
Here is the example I use when explaining why I no longer have contact with her.
When I was 11 I took my first 'cello exam. My dad took the results letter to work as he knew she would open it and it was adressed to me (this is a definite indication my father knew what she was like)
He got home, gave me the letter, she snatched it off me opened it and told me I'd failed.
My dad was confused thinking that surely I wouldn't be entered into an exam that I couldn't at least pass and he then told me I'd passed with a very high distintion.
Meanwhile, I was left in tears wondering why she did that.
I wrote a letter, similar to the 'confrontation letter' described as I felt I had to tell her exactly why I did not want contact with her anymore (after years of verbal and emotional abuse) I felt she could then never say to me that she didn't know why or I had never given her the chance to explain or apologise. Her reply was 'do we have to keep going over this?'
I feel very much at peace with my decision not to have her in my life and always respected my brothers' decisions as to whether they wanted contact or not (They don't)
My dad is equally difficult in different ways as he never stood up for me, is incredibly sexist and constantly hints that he is disapointed in the way I have lived my life (I chose not to become a 'cellist and left music college)
I think, sometimes, there is a need to say out loud 'They weren't great parents, they were abusive, they shouldn't have been and I feel I have to let them know that I know what they did.' It's what you do after the confrontaion letter that is really the important bit. Cry, scream, rant and rave about how unfair crap parents are, but then move on with your life, learn from their mistakes and don't repeat the cycle.