The problem with this argument is that the gangs are already into other things and it is profits from marijuana that are helping them do that. In the context of Canada, marijuana profits and sometimes even marijuana itself are providing the seed capital the gangs need to expand operations into the States, for example, and to diversify operations (e.g., cocaine, heroin, human trafficking and guns). This is one of the main reasons why we need to nip this in the bud.
Do not take my word for it though. Take the RCMP's or VPD's or any police force that you can think of.
Allan Castle, head of the RCMP's criminal analysis section in B.C "B.C. bud . . . was really the industrial revolution of organized crime in B.C.," Mr. Castle said. "It made a lot of bad guys very, very wealthy. And it developed international networks that hadn't existed before."
Special Agent Jeffrey Wagner of DEA "What happens is the organizations, instead of smuggling currency over the border to pay for cocaine to bring up and then again smuggling ecstasy or marijuana over the border, they look at it as a way to pay their debt."
Attributed to RCMP Cpl. Norm Massie "He said gangsters trade weapons and drugs, often with ecstasy and marijuana heading to the U.S. in exchange for guns and cocaine."http://www.bclocalnews.com/tri_city_maple_ridge/tricitynews/news/40814583.html