Councilman Nathan Clay is quoted as saying "explore all sources of revenue... the city needs some income." The council's job is to see that money is used efficiently. What will be done better with more revenue? Or will they go looking for new things to do?
Taxing marijuana sales will create a black market for cheaper untaxed marijuana. Many users are very flexible about where they get their drug money -- theft is popular.
Since the city wants to explore all revenue sources, what will they legalize for how much money? Publish a price list; would they legalize marijuana sales for an additional $200,000, but no less? What would entice them to legalize hard drugs? What revenue would be needed to allow gambling or prostitution? When governments start thinking about money, their ethics seem to get flexible, and the citizens suffer the consequences. Think Chicago, or Las Vegas. It's not a good idea to start down that road.