Terrence McKenna's studies with DMT and the remarkably similar experiences people have with it - encountering the "machine elves" as he calls them - hardly qualify as being told "exactly what they believe".
People have remarkably similiar experiences when they take alcohol. It would seem your skepticism is broken. You really can't conceive any non-natural explanation for this? Remember Occams razor, my friend. Experience tells us that pretty much every claim of paranormal or supernatural activity ever properly investigated is complete hokum, whilst science works. People hear voices in their heads and see things that don't exist without magical creatures mindraping them*.
Your problem, really, is that you're still refusing to acknowledge the difference between subjective and objective reality. You keep conflating them, and claiming that subjective experience is part of objective reality.
I really don't think I should have to explain this all to you, but here it goes. Objective reality is the empirical 'classical' world, the world of physics, mathematics, chemistry and so forth. It's the environment we all share, however, none of us has the same perspective on it: each of us sees our own individual perspective: our subjective reality. Each of us has sets of filters through which we view objective reality: our language and vocabulary (both linguistic and semiotic), our ethics, our political views, our spiritual beliefs. We then process the filtered information and use it to amend our filters, with the idea of trying to find one that fits, and makes sense of the world. However, even if we find such a viewpoint, it is still within us, not a part of the outside world. The most important thing to remember, however, is that information arises within subjective reality
without existing in objective reality. This is otherwise known as your imagination. What I am saying is this: internalised experiences have no objective truth. They may be incredibly meaningful to you, but they don't prove anything. There are thousands, maybe millions, of Star Trek fans who have imagined flying on the Starship Enterprise, but that doesn't make the Enterprise real. The only way for subjective reality to affect the objective is through a human agent.
*HINT: A GOOD WAY TO SEE AND HEAR WIERD SHIT IS TO TAKE DRUGS.