1) What theacidtest said is true in every regard.
2) They sound ignorant, so I will assume what you said about them sounding intelligent was sarcasm.
3) Please explain to me scientifically, preferably with sources cited, how amphetamines at all display certain CNS depressant characteristics as their part of their primary effect - this counteracts all scientific facts ever written; and also please explain how it directly correlates to psychedelics.
Every CNS stimulant has been associated with psychosis when approaching overdose or overuse amounts, the two primary examples being amphetamines and cocaine. I'm not going to get overly scientific in this thread. Amphetamines generally work to increase the amount of dopamine and norepinephrine regarding dopamine and norepinephrine receptor sites. Cocaine is similar, in the effect at it stimulates neural pathways in a similar fashion, yet different, by inhibiting dopamine reuptake at neural transmitters, primarily at the D2 receptors from what I have read, again primarily affecting dopamine. It also inhibits reuptake of serotonin at the 5-HT3 receptor site, which I would assume contributes to the less jittery effects of cocaine compared to amphetamine, especially amphetamine's L-isomer.
Psychedelics work in a completely different regard, and generally are completely unrelated to dopamine and largely affect the 5-HT2A serotonin receptor, replacing serotonin at that receptor and certain others, which is what makes each psychedelic unique in their respective effects. It temporarily "replaces" serotonin at these receptor sites, which contributes to its mood-altering and both sensory and information perception alteration effects. Due to this temporary replacement of serotonin in the brain, psychedelics have been shown to, in contrast to traditional stimulants, actually decrease activity in certain areas of the brain, primarily what could be regarded as the "filters", allowing more information to pass through the sensory receptors and information processing pathways, and also deactivates the part of the brain involving the ego, or rather the part of the brain which allows us to create our self-identity, and hence separate ourselves from others and our environment.
Psychedelics decrease brain activity, allowing more sensory intake and information processing to occur, while simultaneously decreasing brain activity in the region of the brain which is in charge of ego and self-identity, mostly due to replacement of serotonin in the 5-HT2A receptors, while stimulants like amphetamine and cocaine primarily affect dopamine and norepinephrine which increases brain activity and speeds up one's system, physically and psychologically. Both have been linked to psychosis, but psychedelics have only been linked to psychosis in individuals who were already genetically predisposed to psychological disorders such as bipolar, chronic depression, generalized anxiety, or some form of schizophrenia, while stimulants such as amphetamines and cocaine have been known to cause psychosis in any individual, predisposed to psychological disorders or not, when connected to heavy and/or chronic use.