Watermark is trying to draw a line somewhere, but because he's never used any of these substances he's doing it pretty arbitrarily.
Psychedelics pose no addictive threat. There is absolutely no study that has ever pointed to even the slightest threat of physiological addiction.
In principle, it's hard to see where the line should be drawn (if it should be drawn at all). Pragmatically, we must target those drugs responsible for the bulk of crime. Addicts of heroin, crack, ice, and OCs are considerably more dangerous than any others. Their habits are expensive, which frequently leads them to robberies, carjacking, licking, and contract killing.
There are understandable (if not quite justifiable) reasons for banning the most dangerous drugs, but everyone's list of what constitutes "the most dangerous" is going to vary depending on actual experience with drugs and even among those who are experienced, personal preference will play a factor.
Personally, I find that heroin, crack, crystal meth, cheese, and gac have addictive qualities to the point that the government is justified in regulating or banning them. Some anarcho-capitalists would argue that this infringes people's right to use the drug habitually if they choose, but I submit that after the initial two or three highs, there is no longer a conscious choice on the part of the individual, but rather a biological need and a mental void that only their drug can fill.
Basically, it so irrevocably alters your body chemistry and your thought patterns that it cannot be said that you "choose" to continue using heroin anymore than you "choose" to continue breathing.