A different take:
There seems little doubt to me that psilocybin is a very queer substance. Whether its effect on the brain merely simulates profound spirituality or whether it actually recreates it chemically is a philosophical conundrum we won't solve very soon. But that we recognize it somehow as transcendent, that it can be measured in brain scans as indistinguishable from genuine meditative calm, and that it seems, more than any other chemical, to alert one to the divine: well, these seem to be part of the universe as we find it.
What frustrates me is the cultural baggage of the Leary era, the easy ways of dismissing it, the abuse rather than use, the social utopianism rather than the internal peace. It's too interesting a subject for that kind of treatment. And too important.