As you point out, there's all kinds of good reasons for cannabis to be legal. Last I heard, the earliest evidence we have of agriculture is a pouch of hemp seed 12 thousand years old. It's kind of synonymous with human culture.

But you settle on the best reason: we are free. No one has a right to tell us what to think, be, or do, and telling us we can't ingest cannabis is all three.

Thanks!