The funny thing about this is, while I definitely don't believe it in the moustache-twirling-government-villain sense of the mind-control variety, I do think that it's a least _a little_ true - particularly with how public use of LSD may have played an important role in the anti-war movement (Vietnam War). It's widely documented that many people attributed it as a turning point.

Not even that many people need to have tried it; it's one of those consciousness-raising things, where people that you'd normally respect the opinions of start espousing this belief, and that reduces cognitive dissonance in others in a kind of "belief wave".