Greetings,
Well, the author of that article clearly knows very little about drugs. Fair enough, it stands to reason that drugs would be forbidden in Islam, but why does the author feel the need to make assertions that are blatantly untrue?
Marijuana has sedative and mildly hallucinogenic properties. Having said that, no-one ever sees completely illusory objects after smoking it, i.e. you don't suddenly start seeing things that are not there. That could happen with a very strong dose of LSD, but even then full-blown hallucinations are rare.
Cocaine is a stimulant with no hallucinogenic properties.
Opium is an analgesic (painkiller) with no hallucinogenic properties.
So, what the author here claims to be well-known is actually untrue for two of the substances he mentions, and in the case of marijuana, highly debatable.
Please check the facts before posting such misleading propaganda.
Peace