The owner took a poll and the staff discussed it, the staff were not comfortable serving her following the child separations. I believe there were also other customers complaining and trouble starting both inside and outside the restaurant. So it extends to a safety issue, taking it out of discrimination territory, as well as moral.
A business does have a right to refuse custom. Sanders said she was refused service "because she works for POTUS" but it wasn't this, it was specifically the border and child separation issue, which she is part of by staying in her role. She doesn't just work for the president, she is part of the policy in this case as she presents it to the press and defends it.
So the owner took what they described as a "moral stance". Not a political one i.e. no republicans/democrats, but a moral one. I think that's the difference.
Yes the supreme court did rule in favour of the baker and the wedding cake for the gay wedding, religious freedom was the reason given by baker for right to not create what was considered art for a purpose contrary to religious beliefs. Now, without getting into cakes being "art" or "religious freedom" being allowed to exclude, that was the nuanced legal interpretation and the ruling was very narrow i.e. just about this one case so the Justices didn't create something that could be quoted as precedent/new law in many situations. I didn't personally agree that it was a particularly "christian" thing to refuse service, but legally wishing limited scope it was allowed. Baker also doesn't bake bachelorette party style cakes, so it wasn't only gay people focused on, not that this removes discrimination. That was a bizarre only in America case for me.
Also is different as Sanders is not working based on her "religious freedom" nor is anything she does "art".
Religious freedom, restaurant staff and owner believe in humane treatment of children, Human Rights groups have spoken out saying the child separation is inhumane and "torture" re young children isolated. So religious freedom to say don't believe in torture/mistreatment that is being internationally recognised as such and will not serve those involved.
Sanders is being criticised for using her official twitter white house account to complain about a personal incident, because this is not allowed.
Every day more crazy.....