Health risks associated with tobacco and alcohol compared to the risks of cannabis use (not one reported death);behaviour of drunk people in comparison to 'stoned' people; addictive potency of tobacco and alcohol compared with non-addictive cannabis.
Cannabis is clearly less damaging physically than tobacco or alcohol, all the research suggests it. If it wasn't the case that 80% of crime (stats given by policeman, may be inaccurate) was committed by people under the influence of alcohol, then even still it could be argued that cannabis is less worse based on the physiological effects.
tobacco is laced with dozens of highly toxic and carcinogenic chemicals tied to a fibreglass filter known to cause oral lesions.
crimes fueled by alchohol tend to be more violent.
neither of them has a bona fide medicinal purpose.
marijuana has benefits for pain relief, appetite regulation, anti-nausea, neural regulation (as in the treatment of tourette's syndrome). crimes fueled by marijuana tend to be less violent.
Both alcohol and tobacco are very harmful substances. Extensive studies on cannabis have shown that it doesn't cause nearly the health problems that are attributed to both alcohol and tobacco. Besides, when was the last time you saw cirrhosis of the liver in an old Hippie? There have been no published major issues with cannabis (and there have been numerous problems with both alcohol and tobacco), and I know many old stoners, and they are healthy as horses.
Not a single death has come from cannabis consumption alone, meanwhile alcohol poisoning kills hundreds yearly, and no one needs an explanation of how tobacco can kill. While THC is stored as fat in the body and can be easily dispelled with minimal if any side effects, alcohol actively damages the liver and kidneys and tobacco, even if just chewed, causes harm wherever it touches. So while surely all three cause harm, cannabis is causes the least.
Alcohol and tabacco have caused more deaths then cannabis has or ever will cause. Tobacco is a known carcinogen causing various types of cancer to the lungs, esophagus, throat and mouth. Alcohol is known to cause liver damage and highly impairs the judgement of the individual. The only thing cannabis does is endanger a bag of chips.
Whether it be alcohol, tobacco or marijuana, the person using it is looking to alter their physical state to such an extent that their emotional state will also be affected. People drink to forget their worries, they smoke to calm down and use cannabis to mellow out. Therefore, none of them is better or worse than the others, nor are any of them good or bad in and of themselves. It is what humans do with them that determines all.