I never knew Dean had a drinking problem. But when I watched the "Dean scream" with my mother for the first time, I told her, "You know, he looks like a drinker". She said, "You know, you are absolutely right. Maybe that is what is wrong with him".
What's past is past. The thing is, he still seems to act like one. I've known angry drinkers.
If he still has a drinking problem, that's good reason to be concerned, and to bring it up. If it's past, well, he obviously has some current problem...