But my feelings are not relevant and neither are yours. The only person who can decide whether to drink or take drugs is the person themselves, and we cannot stop them.
I think this is a load of rubbish. Social pressure and social attitudes are an important and influential part of society and have the power to make huge changes. For example it is now almost totally socially acceptable for mother's to work or people to be gay or to have sex outside marriage when going back 40, 50 years they were not really acceptable or completely taboo.
It's not always a negative thing, social attitudes have made it unacceptable to be openly racist or homophobic.
I would say that doing something likely to cause another serious harm like drinking heavily when pregnant forms a positive part of that, social pressure not to do it forms an important deterrent.