Conservatives, who generally agree on the value of individual freedom, want the government to limit marijuana. Progressives, who generally agree on the value of big government, don't want the government to limit marijuana.
Conservatives, who generally agree on the merits of capitalism, like genetically modified organisms, as long as they aren't researched using human embryonic stem cells and curing people of serious illnesses. Progressives, who generally dislike capitalism unless it is the magical sort that works in a world where regulation of fossil fuels and mandates and subsidies for lousy alternative solutions from 1600 A.D. will still allow capitalism to flourish, dislike genetically modified organisms because they hate science.