To be clear this depends on the drug. Cocaine and heroin are blood-soaked; cannabis, LSD or psychedelic mushrooms not so much. MDMA is probably somewhere in between.
Cartels also deal Cannabis. In Europe, money from Cannabis traffic is then used to set up logistics for bigger operations, like bank heists, prostitution rings, human trafficking and terrorism, and lets not get started about gangs that kill each other and innocent victims when fighting for territory. Illegal Cannabis is as tainted as Cocaine or heroine. That's why it needs to be legalized. Legalization will weaken organized crime.
I'm surprised they are so into human trafficking and bank heists that they do it at a loss and let it eat into their weed money.