Mary,
....if a Witness owned a business and one of their employees brought in blood sausage for lunch, would the Witness have the right to fire them? No, they wouldn't.
I agree completely.
Freedom of religion has always been interpreted by the courts as freedom from religion, too.
A Jewish employer for example, cannot fire a Gentile employee for eating tref
Similarly, the culinary requirements of halaal are no more enforceable in the workplace than the culinary requirements of kashrut