Actually logic would dictate that the easier something is to get, the more commonplace it would be. You legalize crack, meth, etc. then logically there will be more meth and crack addicts on the street. Crack addicts and meth addicts are unemployable. Meth addicts and crack addicts would then have no income to support their habit, so they would be forced to steal and rob to support their habits. It's entirely logical.
Do you even know anyone who has been addicted to crack or meth? I do, and it has ruined not only their lives, but severely affected everyone's lives around them.