Secound, methadone is an awful drug primarily prescribed for it's much longer half-life (compared to diamorphine/heroin). This makes it more convenient for the ones who are tasked with controlling the traumatized persons intake of the medication. Diamorphine is less physically addictive than methadone and features considerably fewer side effects.
Alcohol is more damaging to the body and harder and more risky to quit than diamorphine. This fact is easily overlooked because the drug is so ubiquitous and socially accepted in our culture. The recreational and casual use that we observe in everyday life makes us believe that alcohol is a less dangerous drug.
Alcohol and tobacco are among the hardest drugs we have, it's just that we are so habituated to their use that we falsely believe they are safer, less addictive and easier to quit once physically dependent.
Heroin, meth, etc. might kill you quicker and be more unpleasant to administer with more noticeable withdrawals, but if we're talking about ultimate cost to society they're not the worst offenders.
I volunteered at an addiction and methadone clinic for awhile. I recommend you try it then come talk about what “hard drugs” are.