Obviously you're misinformed...
I have worked with people with schizophrenia as a result of drug abuse. One client had paranoid schizophrenia from the abuse of cannabis. Don't get me wrong, I have tried and enjoyed it but after seeing what it can actually do changed my opinion forever.
Cannabis is not harmless. It lowers the inhabitions and causes mental illness. If the drug were to be legalised, mental illness would increase, there would probably be more issues such as road accidents and such.
I appreciate your efforts but working closely with the victims of the long term side effects has proved you wrong.