LSD certainly kills people, but it's down around the danger level (to the user) of Cannabis or Ecstasy. Much safer than scary drugs like alcohol or cocaine let alone even worse ones (to the user) like Meth or Heroin.
Alcohol is far worse than Heroin or the other opiates. Nearly all the problems with opiates relate to having unknown quantities due to the lack of regulated producers. The opiate side effect profile is rather tame, mainly constipation. (Apart from respiratory depression, and the unfortunate people that get nauseous.)
The most heinous thing about opiate overdoses is that there exists a drug (Naloxone/Narcan) that if administered in a comfortable window of time will completely negate the effects of the overdose and there are still states in the US that don't condone or approve of its use among drug addicts.
It's available in Australia at the needle exchange. You do a 1 day course as a training session, and you're allowed to purchase it. $5 for three doses, which is pretty great.
There is one more issue with many opiates, which is actually inherent to the drugs and not to the regulatory/market context - the relatively quick gain and loss of tolerance, and the uncertainty this introduces as to the actual physiological effects even of a known dosage.
This is why there are many opiate overdoses where the victim is starting to use after being sober for some time - they go back to the doses that were normal for them not so long ago, but their body chemistry has changed enough that those dosages are now dangerous.
Well that's still rather related to legal issues. If opiates didn't have legal issues, then the social stigma would drop and people wouldn't need to go on these binge rehabs. Also note that other very popular legal drugs require care when going on or off. Eg benzodiazepines can cause death if suddenly discontinued. SSRIs also require care when stopping. Yet these two groups are the most prescribed medications, ever.
Sure - and some opiates (including ones with dangers of addiction and overdose morphine) are themselves prescribed, carefully. But they're not safe on the same level that, say, marijuana or LSD are.
Right I'm just objecting to classifying opiates as the evil hardcore drug, the personification of bad. Alcohol is far worse. In fact, opiates are one if the current post human steps we can take to a Culture-like humanity. Being able to turn off physical and emotional pain, on-demand? Until neuroscience gets us there, opiates are a good start.
I can't read that paper (because of the paywall) to figure out how how they determined the cause of death, beyond simply measuring LSD in the body. http://www.erowid.org/chemicals/lsd/lsd_death.shtml says "LSD was listed as a cause of death by a coroner where more plausible causes of death were the injuries received in fights with police officers."
Assuming it were true, it's odd that a PubMed search finds no more recent papers. No matter what, it's decidedly rare. Renee Honaker was believed to have died of LSD overdose. Quoting http://www.wvgazette.com/News/201303090102 :
> Downey said his initial research into LSD-related fatalities hasn't returned very many reported cases. ... Dr. Elizabeth Sharman, head of the West Virginia Poison Center, hadn't researched the case but said it's the first fatality she's heard of in the state.
NBOMe is also a psychedelic, so falls under the general thesis of the OP. However, it's a rather recent psychedelic so cannot be the reason for the prohibition.
http://www.economist.com/blogs/dailychart/2010/11/drugs_caus...
(That list has alcohol at the top but that's mainly due to drunk people's tendency to harm others via driving or violence)