Remember that the first step of the twelve steps is "admitting that one cannot control one's alcoholism, addiction or compulsion". Finding reasons why you are more privileged than others makes this step even harder.
For example: nicotine is much more addictive (has to do with the speed with which tolerance for a substance is increased) than, say, THC. Which is yet again different from LSD. There are a whole host of factors, and a spectrum of "how dangerous $DRUG is".
(disclosure: it's my pet peeve when people make lump statements about "all drugs")
I recommend you reading about the delta FOSB protein. There is promising research towards unifying all, or almost all, addictions with a single, coherent theory. In this light, drugs are really beginning to look very similar to one another.
You can't take drugs 100% safely, but their safety level does vary, and it definitely varies with wealth.
Amphetamines, for example. Rich Americans get prescriptions for Adderall. Poor Americans make meth. Or take opiates. Vicodin vs. heroin.
There are already millions of Americans that started their opioid adventure with oxycodone or hydrocodone, often coming from the "upper spheres". Addiction does not discriminate. Changing the name from amphetamine to Adderal will not give you more control over your addiction. You will have none, regardless of your income level.
You are right about the safety level though, this is about potential short-term complications. Prescription stuff is not contaminated, a doctor can give you some good advice, or a vial of emergency Naloxone.
However, if you are not in such a good financial position, a heroin addiction will almost certainly ruin your life. From the financial burden of the substance itself, to side effects from adulterants and the impredictability of a dose, you roll the dice every time you shoot up.
I guess this depends on your definition of "100% safely", and probably also on your definition of "drugs". Let's assume that "drugs" means "psychoactive drugs". In that case, I'd suggest that you can take a cup of coffee pretty much as close to 100% safely as is achievable for anything in the world that you can ingest. And coffee is psychoactive. So, it is possible to take drugs 100% safely.
Even alcohol can be taken safely: so long as you keep the dose low, and you're not someone with a special sensitivity to it (e.g. an alcoholic), you can have a glass of red wine with pretty much zero chance of anything bad happening.
That also applies to all the other psychoactive drugs in between: speed, cocaine, LSD, heroin, mushrooms, peyote, MDMA, whatever. They can all be taken 100% safely. The key in all cases is always the same: good education and moderation.
All of these drugs can also be abused. You can kill yourself with caffeine too (though unlikely in coffee form - you'd need about 50-100 espresso shots). I recall a story of someone who ate a whole pack of caffeinated candy, thinking it was normal candy, and died.
Shit happens.
Shit happens more often without good research, education and clear guidelines.
Shit happens even more often without good research, education and clear guidelines, and with dodgy suppliers who may or may not be selling you the thing you think you're buying because they're all criminals.
The real culprit in every drug death? The three branches of the government, who have failed to do the right thing on this topic for 50+ years now.
More powerful psychoactives can make education and moderation moot. Then the addictive qualities can drive the user down a well-trodden road. Ignore this at your peril.
I think that"100% safe" is an exaggeration intended to emphasize that the risk is manageable and it would be more polite to simply state that many substances can be ingested with minimal risk.
Also, withdrawal is not the major problem when combating addiction.
I do personally know someone whom personally knows others who have directly experienced (high dose cannabis edibles for alcohol addiction). There are many claimed first, second, and third hand reports out on the Internet. There are also quite a few professional documentaries about the topic, many amatuer videos (directly capturing the experience and the people involved). I have also come across some peer reviewed literature as well.
I don't maintain a list of such reports and can't look for them at the moment, but they shouldn't be too difficult to find if you are interested.
It is not 100% effective. Some will definitly not change their behavior much, even though they claimed to want to.