I find people harder and harder to understand, the older I get. I was brought up to believe that people had different beliefs and a lot of what they believed was influenced by what they experienced during their lifetime. In school we had classes that were geared just to the beliefs of others, e.g., comparative religions, comparative civilizations, and that included comparing customs. It was the period when a discriminating person was a careful and refined individual, not a bigot.
This whole Balboa Park Nativity scene thing seems as dumb to me as denying the fact that some people display a Star of David or a Menorah. I think everyone loses when children are deprived of the opportunity to compare.