The LD50 of THC is about 1/10 that of alcohol.
While it is difficult to consume an LD50 by smoking marijuana, it is very possible by some of the other forms of consuming THC, like vaping. Vaping of THC, moreover, is linked to the recent spat of vaping deaths.
We also cannot overlook the brain damage caused by THC, especially in younger users (less than 25-30 years old). This is a serious concern, as those who are brain damaged are likely to be burdens on society for a long time.
Evidence?