I'm sure they would try to turn away any middle class homeowner who hasn't bathed in months as well.

I think it's reasonable to have some sanitation and pleasentness standards in a restaurant. Anyone from any economic class could meet or not meet those standards. It may be harder for a homeless person to stay relatively well kept, but I don't think that is the responsibility of the restaurants to fix. We should reduce the people living in filth, not accept and encourage filth I'm public spaces.

Who said this person hasn't bathed in months? I have to challenge your claim of it being fine to want "pleasantness" or "standards" in a public space. 60 years ago, pre civil rights, this "pleasantness" meant not being black, which is ridiculous. "Filth" is also very much culturally shaped ... it sounds like you are saying homelessness == filth && unhealthy && public menace, which is very problematic.

edit: also, the no-cash policy does not filter against the "middle class home owner who hasn't bathed in months", so that does not hold.

That's what price and classiness does, doesn't it? Isn't price the ultimate barrier? Isn't that why Facebook and friends are so effective, because they want to subsidize everything?

More interesting would be to get a business license you must supply services to different tiers of pricing access.

Behavior, not people.

Is a policy which discriminates against cash usage the best way to screen against the "behavior" of being dirty/smelly? Why not just ask him to leave if he loiters too long?

Instead, this policy clearly screens against a group of PEOPLE (those without access to electronic means of payment), which may or may not overlap with those participating in the undesirable "behaviors" I agree a restaurant should have the right to not tolerate.