People don't die from cigarettes... they die from lung cancer caused by smoking cigarettes.
What Ozzy was illustrating is that if you smoked pot for XX years you could still get lung cander and die, however, most people who smoke pot often also smoke Cig's. SO what OZzy is saying is that even though they may smoke cigs as well as pot, the pot may increase the speed at which they get lung cancer, and since they smoke cig's it's blamed onthe sig's rather than the pot. Also, if you smoked pot as much as some people smoke cig's I am pretty confident you'd get lung cancer as well.
However, my grandmother was smoking 2 packs of slim-longs every day for about 15 years, and has been smoking since the 40/50's (? not certain when she started) and she does not have lung cancer and has not been placed under watch for it because her lungs are still i reasonably good (though still old) health. SO one could say that if she smoked pot as well that she may have lung cancer by now.
ANyway... uhh... I agree with Ozzy; Pot can kill you if you smoke it too much, it has just never been proven in anything more than lab animals.