Religion, national origin and race are protected by the U.S. Constitution.  Members of these groups should be afforded the exact-same rights and accommodations as every-other person in this country.  No more and no less.  That's the way it's supposed to work.  When these folks were brought in to staff the plant, I imagine it was a quite a shock to the existing workers, and would have taken great effort to assimilate them.  I just don't think this whole thing was well-thought out. Two interesting things here:
1.  Why would Muslims choose to work in a meat-processing facility?  They aren't allowed to eat some of the meat.  It's similar to the Muslim woman who was a waitress in a restaurant, but couldn't serve alcohol because of her religious beliefs.
2.  The ruling also addresses the fact that the union failed to protect them.