Just to be clear: what makes me furious is the idea that someone would harm themselves in such a way, and yet continue down that path in a misguided journey of self-discovery (or whatever).

I've had some very similar experiences to yourself and I'm not against using drugs, per se.

But. When you say stuff like "what you think of as depth perception is but a shade of what I saw then", or "I've seen a shade of green that you probably haven't", you cannot separate what you actually perceived, and what your brain thinks it perceived. Exactly so: I'm either a great singer when I'm drunk, or I think I'm a great singer when I'm drunk.

Using drugs safely can be a lot of fun. But I take all of those experiences (including my own) with large tablespoons of salt.

EDIT:

Feel like I should add another point. Perception is everything. Your stone-cold-sober perception is just one possible state. It's the best we have, but I still barely trust it.

The biggest revelations for me, have always come from hard science. Quantum physics blows my mind, cosmology blows my mind, heck I did a degree in Physics because I was fascinated. I've never beat the lasting awe for reality, with anything that, for all I know, is utterly fake.