Why do they ban wal*mart in california?:
Well, for one thing, Wal-Mart has one of the worst ratings in terms of how they treat their employees.  I know people who boycott them and have encouraged me to do likewise.
They are not like Costco at all.
Why would Californians want to encourage a store to treat its peopel poorly?
Why would they want to pay when the full-timers get cut back to part-time, lose their bennies, and go on Medicaid and use state-supported supplemental insurance plans (I'm assuming; I'm from NY)?
Why would they want the related stress that comes with the anger and worthless feelings of being in such an environment so many hours a week?
Why would they want them around at all?