This boils down to a two question "should we as society allow a person to destroy his life." And because there is also a big external pressure from financially interested parties to convince a person to do things that are not beneficial to him, second question is "should we as society let smarter people fool less educated people out of their money/health/ happiness" (second one is more tricky) but low hanging fruits are advertisement for alcohol, gambling, smoking and other obviously non beneficial activities.