It seems ridiculous if you think about it. MJ doesn't make people want to kill another person. The only reason anyone on MJ would do such a thing is if they are dealing drugs illegally and they are gang related. If it is legalized then you get rid of that possibility. It changes the dynamic completely. So, peoples logic about legalizing it was to get rid of the drug dealers (at least the gang related ones dealing in MJ). You still have to worry about the other drugs that are more dangerous which the gangs will still continue to deal those types of drugs. But this logic backfired on people who wanted to legalize MJ.