Just because you're "pro-pot" doesn't mean you're a smoker of pot. There are countless ways to ingest THC, whereas cigarettes have to be smoked to be ingested. In fact, you can be pro-pot, and hate any and all types of smoke. See how that works?
There are also many people who are pro-pot (and not even users) because of the cost of criminalization to the citizens both financially and socially. Currently the US spends $10 Billion/year criminalizing marijuana, and yearly arrests are more than murder, rape, robbery, and aggravated assault combined. It's beyond goofy that it's classified as a Sched. 1 drug. What's a Sched. 1 drug? "The drug or other substance has no currently accepted medical treatment use in the U.S." Ha.
So it doesn't take a mental giant (to borrow from you) to easily see how one could be pro-pot and anti-cigarette.