He knew what it was like to lose your parents and to watch it happen. Bruce also knew what it felt like to think that you were the one responsible for what happened. The responsibility went to the person who decided to take their life and set her up to be there. Just like it was Joe Chill's responsibility for killing them...not Bruce's for being scared and needing to leave the theater.
The problem was the longer you were left in that numb and angry space the harder it was to feel anything. Somehow he didn't think Rachel's tactic would work in her case.
"It's not your fault. Whether you believe that or not. You didn't choose the wrong door someone else chose to set you in that position."