I totally agree.
I am very big on freedom.
In the interests of efficiency and freedom for customers, would expecting merchants to post signage, explaining exactly who they will serve and what they will do, be too much to ask? And expecting them to serve whoever asks them for something they advertise, if the merchant didn't publicly post their unwillingness to do so?
Put up a sign on the door. "No Blacks, no Irish, no gays", or whatever. Just make it clear to everybody before they go to your business.
Tom