I think it's a bad law, but surely not as bad as you originally tried to mislead people into believing.
> Is there really a way to overstate the insanity of state-sponsored killing people for this?
Apparently yes, by intentionally making a false claim that you get executed for smoking a joint.
> Please let's not stray too far from the subject of, what justification for killing this drug user are you looking for?
They won't get executed for being a drug user, but for trafficking drugs. Given that 500 grams is a huge amount, I think it's reasonable to consider the offenders to be drug traffickers (even if I don't agree with the punishment).