I know that’s what some people claim, but different people will react differently to the same drug, marijuana included. Some can feel empowered, some feel paranoid, some mellow, some delusional. And that just becomes amplified with greater usage over time. I’d expect it to be worse with “harder” drugs, but then it’s just an argument over degrees.
I've always found it rather ironic that so many drugs used to treat depression have explicit warnings to seek medical attention if experiencing suicidal thoughts.
I used to smoke pot. Most of my friends smoked. Have probably met hundreds of smokers. None has ever shown a trace of violence. Mostly they sat around, listened to music and ate non-stop.
Never heard a single connection between pot and violence or delusional or anything bad other than some getting paranoid from it, but the paranoid ones just stopped smoking.
Compare to the amount of mayhem created by those who drink alcohol. I drink a bit and the only stupid thing I ever did on drugs was drive drunk once. Luckily nothing happened.