Lets say, for example, one uses heroin non-intravenously and in controlled doses, in order to treat his depression and social anxiety, is it really "wrong"?
There is so much negative connotation on heroin that the moment someone hears the word 'heroin', all they think about is criminal, dying drug addict, junky, dirty homeless jobless man or a prostitute, who needs help.
Then if LE hears the word they just want to bust down the door to arrest the hardcore criminal. WTH, lets say one is just using it responsibly for health purpose without commiting crimes of hurting anyone, do you think the law can be lenient before labelling it as an offence to even use heroin?
It's not inherently wrong to use heroin. It's just an incredibly addictive substance in comparison to other substances (weed/lsd/mdma etc.). It's physically addictive and if you have issues in your life it can definitely be psychologically addictive as well.
So it's not "wrong" to use it, it's just easy to spiral down to a path of tolerance and increased doses & frequency. Nobody's stronger than addiction.