Do you really think that marijuana is the only drug you can grow in your backyard? Do you think it is the only drug that can easily be grown that also has medical uses? The drugs described in the article could be grown and purified at home.

"There are plenty of chemical substances of substantial and extreme harm"

Care to actually name any?

Really, you are approaching drug policy from entirely the wrong angle. The DEA is a paramilitary agency, one that has the power to declare drugs to be illegal without any democratic process at all, and which has the legal authority to seize property and then use the proceeds from the sale of that property in its own budget. Thousands of innocent people have been killed by DEA assaults on civilian homes, for being in the wrong place at the wrong time or just because of bad information from informants. Health and safety are, in practice, completely irrelevant to the DEA.

That the DEA works for the benefit of the pharmaceutical industry is not in question anymore. The Obama administration released emails related to the healthcare bill that paint a clear quid-pro-quo picture: stronger DEA action against illegal drug imports and medical marijuana programs in exchange for pharmaceutical lobbyists supporting the bill.

"some drugs are wrongly regulated"

Almost all useful drugs are wrongly regulated. There is no recognition of the reality that recreational drugs will be used regardless of the law. This has not only led to a steady source of income for criminals, but also to terrible tragedies in the past. In the 1980s, several people who wanted to use heroine developed Parkinson's disease after a drug dealer attempted to sell a legal alternative, MPPP, but so accidentally produced poisonous MPTP, a Parkinson's-inducing agent (ironically, MPPP is now illegal; MPTP is not illegal, despite being one of the most dangerous substances a person can ingest). Recreational drug users have no way to know what dose or purity they are buying, nor even if they are actually buying the drug they expect, with only two exceptions: alcohol and tobacco.

So when a drug user goes to the doctor, what can they say? "I have been ingesting a white powder some criminal sold me. I think it is cocaine." That does not promote public health by any stretch of the imagination; by contrast, an tobacco user can tell their doctor about their habit in a way that is useful: "I smoke a pack of cigarettes each week," or perhaps, "I smoke a cigar once every 4-5 months." When some guy is found nude in the woods after having used something labeled "bath salts," we really have no way to know what happened -- did he overdose on MDPV, or was it just a lot of caffeine, or perhaps some drug that we have never seen before?

"let's dismantle the whole system"

You make it sound as though the system established by the controlled substances act has some merit or utility. In reality, it is a system without any constructive purpose at all, which serves only to inflate the profits of certain well-connected corporations, to serve the interests of police and prison guard unions, and to give the government a way to continue to oppress certain minorities despite clear laws protecting people from such oppression. The controlled substances act also gives the executive branch tremendous power, allowing the creation of new prohibition law without an act of congress; this power was recently used to ban several synthetic cannibinoids and MDPV. The executive branch can also overrule the DHHS and FDA recommendations on drug scheduling, having famously done so for MDMA.

So unless you can point to something useful the DEA and the controlled substances act have accomplished, I see no reason to assume that disbanding a combination law enforcement agency, intelligence agency, and paramilitary force would be a bad thing. Repeal the CSA and replace it with sensible regulations on drugs and constructive policies that promote human health, and you'll have pushed society forward.