As a counselor I have spoken with crack addicts who said they wished the MJ was as easy to get as crack, because they would prefer. Since dates are not given there is no way to evaluate whether the increase in robbery and other crimes not to mention the desire to get blotto is due to the world economy going to heck in 2008. When Point Barrow in Alaska prohibited alcohol, the crime rate dropped 70%. People on pot tend to be mellow, not violent unless it is laced with PCP or similar.
Remember correlation is not causation. I am told that in Portugal and Switzerland the results have been quite different when drug laws were lightened.
Also, by keeping it illegal, we cannot regulate it. This gives the cartels the incentive to create drugs that are so addictive that a user is compelled to do literally anything to achieve that high, no matter the price. With legalization, drugs can be regulated to ensure a limit on the high and we can control the high the user gets.
I understand that it was no different with Prohibition. Prior to Prohibition, upwards of a third of adults were in a continual stupor, which was the reason to bring it on. During Prohibition, moonshine was often 190 to 200 proof. It was legalization and regulation of alcohol that eliminated most of the problems.