Our local school board tried to implement a policy that would have prohibited teachers from participating in an after school Bible study for kids hosted by a private group, but in space rented from the school. The concern was that kids might think the school was (gasp) promoting religion if they saw their teacher participating in this program.
The case went all the way to the Federal Court of Appeals with a unanimous ruling throwing out the policy stating that the school district could not in effect limit the rights of teachers in their non working hours.
I see a court challenge to this policy resulting in the same decision.
That is a clear case of religious discrimination. However, you shouldn't take this case to mean that an employer can't fire you for things you do outside of work hours. In most cases, they can.
Nobody cares about this unless they are in the targeted group.I'm sure the responses would be a little different if they went to work and the boss told them they were fired for being religious,Republican/conservative,a gun owner,drinker or any other legal activity one takes part in.