In my opinion, you cannot do anything about that anymore and that is out of your control. It’s the persons personal agenda now and people who have tried something that they had fun and want to continue might have some problems in the future. It’s not wrong to teach them the right thing but it’s up to them to do what is right.
We have individual diversity. As, Howard Garner introduced 8 multiple intelligence. Therefore, we cannot pursue anyone to like what we want. We have different likes, so why do we need to control everyone?
People enjoys gambling but not all of us. As what you have said, it is not wrong to teach them how to gamble as long as we just share some facts with them. But controlling their emotion is not good also since they have rationalization.