I certainly don't believe in telling others what to do. However, I've suggested that people stop doing things that I believe are self destructive, like engaging in hardcore drug abuse or staying in abusive relationships. I might make my case very strongly, but I would never try to force someone not to do something just because I didn't believe it was right. My judgements aren't theirs, and everyone has a right to make their own decisions.

Prescription drug use can be inappropriate and downright dangerous. It can sometimes fall into the above category. Somebody who believed that might make a very strong case against continuing a drug regimen, particularly if they cared. However, you're well within your right to tell the person that you've heard them but disagree and that you don't wish to discuss the topic any further. Everyone has opinions. You get to choose whether you want to discuss those opinions. Arguing with someone is a choice you make that involves sharing ideas.

If a stranger is very insistently trying to force you to do something, then you would obviously just tell that person to go to hell unless you believed they had something insightful to say. I wouldn't take it personally though. Look at the information itself. Personally, if somebody had a bad experience with a drug that I used, I would want to know about it so I could be watchful in the future.

Knowledge is power, not an attack. I would hate to see the day that we didn't pursue information just because someone's feelings might be hurt. If someone feels invalidated by the mere mention that a drug can be dangerous, then that signals a lack of comfort with oneself. If someone isn't being seriously intrusive, and you still feel invalidated by their comments, then the issue is probably with you rather than them. Address your own feelings of discomfort and the root of them.

I don't know which of the above scenarios applies to anyone here. It's up to all of you to judge for yourselves.