Weed is the only one of the four you mentioned that I would have no trouble with doing if it were presented to me, and DMT is the only one that I would definitely not do without more research.
(I do not, of course, recommend anyone go out and try DMT without first experiencing other psychedelics in the order given, or in fact without doing the research.)
I highly recommend you do that research.
Psychedelic use is not to be taken lightly. It is not a form of recreation (shouldn't be), it is a method of deep introspection, of breaking down mental barriers, a journey within yourself (among other things which really cannot be explained until you have reached the state of understanding that usually occurs with mush or mescaline use. This too is not an absolute, but is common to most peoples 'route' in this journey.)
Use of entheogens is, of course, not the only route to these states, tantric yoga can perform the same function as cannabis, and years (or decades) of deep meditation can take replace the use of mush, LSD and DMT.
Hedonism is best served occasionally.
Go with the flow atleast until you understand it.
Some voices are answers, others are questions.
All things are relative.
All things are subjective.
It is only possible to have a bad trip if you convince yourself/believe/decide you are having a bad trip.
Take _nothing_ for granted or as absolute.
Words are unreliable.
Do not be afraid to depreciate the mental monologue.
Do not be afraid.
Seriously, that seems to be the worst side-effect I've noticed of most of these drugs -- they grant an unjustified feeling of the profundity of your own thoughts.
He's clearly formulated his opinions after deep thought, and I find it pretty interesting, personally coming from a rooted Zen and Hindu perspective, how some of his ideas echo the thoughts of great religious thinkers (for example, "All things are subjective" is held as one of the basic axioms in Zen philosophy).
And perhaps he is just simply repeating the ideas of others. At least he appears to understand (or at least is clearly making an effort to) wisdom that has been imparted through the ages and is generally acquired only through deep introspection.
Check your preconceptions at the door-- it's pretty clear that you dismissed his ideas based on your notions of what "these drugs", and the people who use them, must be.
The grandparent has dismissed what I said as 'crap' created by my 'unjustified feeling of the profundity[sic]'. Interestingly, since these words stemed from eastern religion, from philosophy and even from common sense and reasoning (as well as my own personal experiences, and the words and works of psychedelic researchers) all these things too must be 'crap' that could only make sense after the 'delusions of drug use', after all:
"Biggest argument against taking drugs: they'll make you think that crap like that is "wisdom"."
PS: The path of blind rejectionism may be comfortable, it may be culturally encoraged, but as history has shown, it is inevitably a dead-end route.