I have been listening to this same old worn out argument since the 70's. The legalization of alcohol is known. The legalization of pot is not. Children will not be able to legally by the drug so they will be the new target for illegal sales. There will be no reduction in crime and any economic benefit will be absorbed by the increased demand for government assistance in getting off of marijuana. Children will not benefit from parents who are high.
There is no upside except for those who are already smoke pot and would like to make it legal and cheaper.