Every store/business owner should have the right to decide who they serve as long as they do not have a monopoly (power companies etc). I am totally fine with this stores policy, of course I wouldn't go there but let them do as they wish.
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It doesn't work both ways. If they said blacks needed a deposit and whites didn't, that would be considered racist. But, the way it's written it's not considered racist or discriminatory toward whites. If a white owner wrote the same thing, they would most likely be sued and the plaintiff would win.
Store owners should have the right to decide who they serve. Unfortunately, if they are white, they don't.