Really the simple answer is that if that grocery store doesn't want to cater to the unvaccinated, but were told they couldn't discriminate on those grounds, they could just close for everyone, right? And, if every store decided to do that, what would you do?

The point is you don't have a right to service (no shirt, no shoes, no vaccine, etc). This isn't Soviet Russia. The government doesn't give you a job and tell you to do it no matter what.

Basically, if they want your business, they will concede, but they should not be forced to.

You could always open your own grocery store. Just think of the giant untapped market for the unvaccinated. It's literally the American way.