I call BS. Provide an exact quotation.
https://marijuana.procon.org
2-"Crime and violence, both within the U.S. and at the U.S.-Mexico border, are greatly increased due to illegal selling and buying of marijuana. Legalization would logically end the need for such criminal behavior."
https://www.thoughtco.com/pros-and-cons-legalizing-marijuana-3325521
3-"Legalizing recreational weed cuts off an important revenue stream for many in the illegal drug trade. Advocates of legalization contend that by making the substance less profitable for criminals, it will decrease the violence associated with the trade. "
https://www.drugrehab.us/news/pros-cons-legalizing-recreational-marijuana/
Whew! That was a lot of tough research.....1st three Google entries.....