Cannabis Does Not Harm
Prohibition of cannabis and contaminated cannabis causes harm.
Cannabis is NON-Addictive
People are addicted to the RELIEF cannabis brings to their issues. Solve or remove all the issues and the "so called" cannabis addiction evaporates. There is zero physical addiction to cannabis. Sure is great at relieving a huge number of issues though. :)
By the way... All of the negatives you listed about cannabis are avoidable. I personally grow a strain called Canna-Tsu which does not produce negative side effects. Many of the negative side effects you listed are also caused by contaminates, not necessarily the cannabis. :)