I absolutely agree with hopeful4's therapist on this.
Growing up my Mother did protect us somewhat from the drama - as much as she could.
As teenagers not so much (you can't get a teen to go to bed at 8:00). Luckily my Father worked away a lot so there were a lot of "normal" times in our house.
The result of this, for all of us I believe, is that we completely understood the lay of the land. We understood that the alcoholic was causing the drama and the damage. Therefore I think it helped us to A. See things from my Mom's point of view and B. Understand that the alcoholic doesn't need special care (as in realized this second part later on, during the growing up phase it's very much a matter of smoothing things over and trying to lessen the anger and drama).
If we hadn't seen that perhaps, as adults, we would have continued to walk on eggshells, trying to smooth things over with him. Even with all that we did to some degree, however our coping mechanisms were different.
All that said, this still had an effect. I believe that no one goes through that with no result on their defenses, coping mechanisms, functioning in relationships etc. This is not a "boo-hoo poor me" statement, I have never felt like a "victim".
There is no need to cover for him.