The following is quoted from the bottom of page 450 and top of page 451 of Dennis McKenna's memoir THE BROTHERHOOD OF THE SCREAMING ABYSS
'Psychedelics are not suppressed because they are dangerous to users; they're suppressed because they provoke unconventional thought, which threatens any number of elites and institutions that would rather do our thinking for us... Mushrooms have a way of inoculating the mind against the kind of thought control the prevailing order in any age needs to sustain itself. I'm not naively suggesting that the work of building a better world stops with the psychedelic experience. But it could be where it begins, or is renewed-in the moment of freedom when one glimpses the transient nature of reality and its ever-present potential for change.'