Bullshit.

drugs or any other substance that alter one's perception of reality
Funny, I thought all substances that altered perception were drugs.

Think about this, Serotonin and Dopamine are very important neurotransmitters. Psilocybin found in mushrooms is very similar in chemical structure to serotonin.
A very powerful hallucinogen known as DMT is found naturally occuring in many living things including the pineal gland of the human brain.
If you want to talk about drugs and spirituality, DMT is released by the pineal gland in larger amounts during birth and before death.

Smoking marijuana increases the amount on melatonin in your brain significantly, as does meditation.

Many cultures have used psychedelics for spiritual insight for thousands of years. A thing to note is that with powerful hallucinogens like LSD, DMT and Salvinorin individual reaction to the substance varies widely as if the drugs effects are customized according to your personal brain chemistry, set and setting. There is a big difference between using these substances for mere reaction, and using them for insight.