Leaving aside issues not regarding adults (as underage consumption of many things is regulated now, there's nothing new here to be brought into the discussion), do you really think it's up to you to decide what is good and bad for everyone? Especially as you seem to be vastly misinformed on both personal and societal tolerances of both amphetamines and opiates. While both can be dangerously abused, so can be many common chemicals - like alcohol. There are ways beside prohibitionism to deal with it.