Keep that head in the sand. An addict is an addict. Rush was, allegedly, buying drugs off the street. He might very well have bought his drugs from the SAME GUY selling drugs to addicts in abandoned warehouses. But you'll give Rush the pass.
How many addicts of other drugs used 'pain' as a reason for starting their own addiction? There are plenty of addicts who started due to pain. Then they became addicts. The only difference is the drug of choice.