Well, yeah, but you're looking for objective reasoning. At a certain point it's about ideological archetypes and virtue signaling. Big tobacco = evil corporations spreading death for profit; marijuana = peace and love and groovy rebellion against The Man.
A couple decades back I lived in a small, hard left town. The sort of place that not only declares itself a "nuclear free zone" but posts it on road signs. During the time I lived there, the town council passed ordinances, in the same week and without the slightest sense of irony, banning tobacco use in any form on the town green; and, allowing smoking marijuana on the town green. Go figure.