All these problems that you state about overprescription and users turning to unsafe harder drugs is all due to the fact that these drugs are illegal. The same concerns were voiced about alcohol during prohibition. Now no one treats alcohol like a medicine and they understand it is a drug. Alcohol is a "hard drug" by any definition as it causes dependence and can have a very negative impact on your life. It was even more dangerous when it was illegal.
The choice isn't between making drugs legal and having a drug free world. The choice is between making it legal or spending resources throwing those who choose to use drugs in jail.
[0] http://www.economist.com/blogs/dailychart/2010/11/drugs_caus...