I think the FAs should be allowed to wear whatever they want as long as it's not part of the uniform. "I love Allah", "I love Jesus", "I love the Goddess of the Volcano", "I love Elvis", sure, whatever helps them make it through the day.
The little AS cards are a bad, repulsive case of a corporation pushing a religion down their passengers' throat. I didn't ask to be preached to when I asked for that sandwich. Bad.