Well, four people were studied for smoking pot for 11 to 27 years, and only two had slight pulmonary changes, every single other factor of their health remained the same.

That means that Cannabis goes 4 for 4. Did you see how extensive their tests were? If Cannabis was that bad, then at least 1 of the subjects would have turned out with ill-effects.

A study was done on Cannabis being bad for you, in the long-term, and all four subjects turned up healthy. Do that study with Heroin. With Cigarettes. Do it with foods, high in cholesterol.