Face recognition camera at entrance, shared database between stores, two door turnikets, armed guards at entrance... Boom! Problem solved!
0: https://www.cbsnews.com/sanfrancisco/news/bart-withholding-s...
And said businesses will blasted all over the news for being racist (because there's going to be a _very obvious_ pattern of who is denied entry). Which takes us back to square one. No business is going to want to be a party to the inevitable shitstorm that will come of it.
If anything this system can be promoted and sold as barrier from right wing extremism. Now you can physically ban tump supporters and antivagers from your shop!
Edit: also shop owners and security can be black...