Nowhere have I come across any research that has pointed towards a connection between the intensity of cannabis and violence. Violent outbursts could somewhat be true depending upon the mental state of a person smoking cannabis with high THC content like giving strong cannabis to a schizophrenic but that wouldn't be the fault of cannabis, only the fault of giving a psychoactive drug to a mentally unwell individual.
The availability of alcohol doesn't matter. Looking at areas such as Colorado also proves there is no connection between cannabis dosage and violence.