I believe that if someone really is comfortable about the way they live, they won't have a problem listening to a stranger telling them otherwise and just forgetting about it in a hearbeat.
Personally I think it would be better for society at large if people spoke up what the thought about the behavior of others more often. It doesn't mean that you have to follow everything you are being told, but it would give you some "precious" hints about what is going on.
HTB.
I simply cannot believe that people actually feel it's OK to go up to a complete stranger and tell them anything like this.
I hope those people walk up to every smoker they encounter and confront them with the news that smoking is killing them. Somehow I doubt that's happening.