Los Angeles has thousands of problems that are far, far more important than banning plastic bags and paper bags. First of all, people are under the impression that most paper comes from natural woodlands. It isn't. It comes from trees that are grown specifically for making paper, kind of the same concept as Christmas tree farms. Secondly, plastic bags are recyclable.
Unless you launder your cloth bag after each and every time you carry meat, especially chicken or turkey, you run the real risk of a bacteria transfer to other foods.