Funny story about the Soviets...

The U.S. spread propaganda that cannabis would turn Americans into radical pacifists docile enough to be easily subjugated by Soviet invaders.

Apparently, the Soviets only banned cannabis because the myth became so prevalent in global political circles that they became scared of the same thing.

It's because humans, as a species, are threatened by cannibus because it had priority over the Earth. First come, first serve.