By that logic burning incense is dangerous.
You'd have to smoke a fucking hell of a lot of weed to come even close to the amount of inhaled tar as cigarettes. And as the study suggested, THC in itself has regenerative properties.
This study was made by the same exact man and group who did the studies finding previously proving that weed = cancer, but as the article points out the old studies were MUCH smaller, and this MUCH bigger study proved the opposite.
I bet smoking one joint a week would be equivalent to burning a stick of incense a day for a week. Just guessing of course. Hell, I don't even smoke joints, it's too wasteful and the paper itself is harmful. I stick with pipes, like most potheads. Add to that the effect of a bong, which uses water to cool down the smoke, and you don't even have to worry about burning your throat.