Post Praetorian said:
When a common morality is absent from neighbors might not such misunderstandings be expected to multiply?
Yes, and force discussion where otherwise such a discussion might be considered taboo. However, just because a common set-in-stone morality might not exist, that is not to say that a common set of laws for a given region shouldn't exist. The lawn ornament thing sounds pretty minor, and not really so much about moral misunderanding as it is about the local code of behavior. Most people can adapt their behavior to match a local set of rules, so long as they don't egregiously violate the fundamentals of their own moral code. It is hard to imagine that this family couldn't easily adapt when informed of the discrepency.
For instance, if I were to visit certain countries, my wife would be expected to wear a scarf - I'm sure we could adapt to that out of respect to the local code of behavior. It would be a different matter altogether if we were to vacation someplace with an extreme religion, and be required to stone a heretic. In that instance, if there weren't such a cast-in-stone morality based on some sacred verse, maybe I would be able to respectfully question the practice without getting stoned myself.