Drug addict won't suffer from withdrawal symptoms if u don't
withdraw drugs from them. The problem is that smokers are
everywhere, they harm ppl who don't smoke. Furthermore, passive
smoking is more harmful than smoking it yourself. Also, smoke
addict suffers from withdrawal symptoms.
There is somethign very wrogn with your concept. Heroin and
cocaine user suffers much more sever withdrawal symptoms than
cigerrettes. An example is heroin, its withdrawal effect include
aches and spasms, stomach cramps, vomiting, runny nose, watery
eyes, loss of appetite and loss of body fluids. Furthermore, no
matter how much passive smoking u inhale, your health is still in a
better state than those taking heroin or cocaine
http://www.nida.nih.gov/Infofacts/cocaine.html
http://www.nida.nih.gov/Infofacts/heroin.html
Smoking is a mild addiction? don't make me laugh. Nicotine is as
addictive as heroin and cocaine.
But is less harmful than heroin and cocaine 
I don't know if heroin is more harmful than cigarette but heroin
is easier to quit and less addictive than cigarettes. Why? because
a smoker delivers 200-300 discrete doses of nicotine(the addicting
agent) to the brain and a heroin addict delivers only 2-3 doses of
nicotine to the brain.
Nicotine is not the only thing in the world tat make u an addict

So you kill a heroin addict who was a better chance to quit his
habit than a smoker? You let a heroin addict who can only harm
himself die? Then you let a smoker who can harm thousands of lives
for the rest of his life live?
No, the abuser is never killed. The drug trafficker tat sell
drugs to the user r the ones tat get killed. 
A Fried Cha Kway Teow seller probably cause more more harm to more
people than a smoker for the rest of their life also live as well.
