Okay, so I used the wrong word. (I only used it once, btw.) But if you saw your neighbor’s kid smoking drugs, or with needles or whatever, would you ignore it and do nothing and notify no one because “it’s none of my business”?
If damaging one’s body (which we have temporarily) warrants intervention, so much more so when damaging one’s neshama (which we have permanently) and olam haboh demands it.