Consider:

1. People often say “It’s not personal, it’s just business”, or “This is personal.”

2. We have laws to discourage discrimination based on gender, race, age, religion, etc., but they only apply at work, school, clubs, etc. and not to “personal” relations such as friends or lovers.

3. Law let’s us sue firms or schools that lie to us, to discourage such lies, but not only can’t we sue our friends or lovers for their lies, law prohibits blackmail, which would otherwise discourage such lies.

What are other key differences in how we treat “impersonal” from “personal” arenas?  What is the essential difference that explains these differing treatments?

My tentative theory: our ancestors had different social norms for “personal” within-tribe versus “impersonal” between-tribe behavior.  When you interacted with someone from another tribe, you had to be more careful to be neutral and inoffensive, since your whole tribe might suffer if you offended someone.