Who says shame is bad? Shame is a negative impact. People tend to avoid negative things. Therefore associating shame with an activity will cause that activity to be less likely to be done.
What actually happens because of such shaming is that they don't seek help ie. they avoid the very things that could help them out of their addiction. That is certainly a negative impact, as you put it. I refer you once again to Loki's first post in this thread.
"One day, we shall die. All the other days, we shall live."