Unsafe... that seems a stretch, uncomfortable maybe... the "unsafe" issue could have been addressed given it was not a surprise event.
If a restaurant worker felt unsafe around a black family, would you say the same thing.
I had to confront employees not feeling safe in the 80s, when many of my staff felt uncomfortable around an employee that was dying of HIV but wanted to still work. I told them all the evidence pointed to the only way to contract HIV was through body fluid exchange... don't exchange body fluids with Roger, meanwhile, you can work or quit, but Roger is welcome to work as long as he wants. He worked up to the week before he died. I don't think he had anywhere else to go.
My point is in our woke society, we have condoned bad behavior against some groups and not others... that is unacceptable.
I would expect my grandchildren if they worked in a restaurant to serve anyone provided the customers acted with proper decorum. I tell them, you have to get along with "assholes" in this world, but you don't have to like them.
We live in a free country and that means tolerating people whose beliefs you find repulsive provided they are respectful.
With regard to the child and the family, I would look at the manager's past behavior. If he had never had issues with African American customers, African American employees, etc., then it may well have been something different. I also believe in giving people the benefit of the doubt.
But as the owner of the business, I would not tolerate an employee that allowed their personal prejudices to undermine the reputation of the company. In this case, I would conduct an investigation, which is perhaps why the company put the employee on leave. If the employee had a track record of racist behavior, he would be gone. But so would the employees that refused to serve the Christian group based on their ideology. In their case, no investigation is necessary as they made it clear why they did what they did. If they could show the group has a history of violence that is one thing, but otherwise the reality is they probably serve all sorts of customers whose ideology they don't agree with and probably don't know.
Not serving someone because they don't share your beliefs is a form of bigotry.