It's a thorny issue courts are challenged to balance and sort out, so I doubt if we will reach consensus on an internet forum
I'm a business owner, nobody tells me how to run it!
(sure they do, see FTC, IRS, OSHA, et.al. ad infinitum)
I'm a customer, same as next guy, I demand to be treated fairly!
(but there are dress codes, rights of association, reserved rights regarding property, alcohol and weapons-on-premisses regulations, etc. and so on)
Some business owners even today still resent being told they have to serve people with a different skin complexion. Some customers demand to enter privately-owned stores serving the public while wielding assault rifles. There are lots bigger fish waiting to be fried besides whether US legal tender is accepted.