I know of "Freedom Of Religion" in the Constitution, but there is no "Freedom From Religion" in it. "Of" and "from" don't have the same meaning. You know that, right?

Business owners aren't required to be atheist, nor can they be prevented from following their beliefs. That would violate a Constitutional right. 

They can't require a religious litmus test, or for an employee to attend services... if it's not church associated employment, and those aren't the issue here. An employer can't ask you about your religious beliefs. An employer can't persuade an employee to be religious (or deny them their religious freedom), by threat of negative reviews or termination. Again, neither of those are an issue here. 

Nobody is being forced to follow anyone else's religion, or beliefs.