@livinglava,
You'd have to understand the turmoil of the 1970's where white rule conflicted with the majority black population. I'm not in no way an expert on Bob Marley, only to say he was seen as a threat to how the masses were controlled.
Naturally grown pot exists in many warm, tepid climates especially southern and eastern Asia. Again, I'm not an expert, however those countries that can cultivate the plant naturally have extreme controls against the growth, cultivation and usage of the product.