You need to take reality into account. The choice is not weed/no weed. It's legal weed/illegal weed.
Same reasoning as about alcohol. You remember the prohibition? Mafia, criminality, corruption, nice people had to be in contact with bad people, no tax, justice and police attention distracted from real crimes, etc...
It's the same for illegal weed: mafia, gangs, criminality, corruption, no tax, justice and police attention diverted from real drug problems such as Yaba and other hard drugs..
Legal weed: nice people in contact with nice people who legally make a living, not with dealers who may try to convert them to hard drugs, police and justice focused on real criminality.....