The fact that you took 'assassination' out of the context of specific reference to various times and places, alongside 'challenge them to a duel' is significant. It made me think back, trying to recall whether you had previously made yourself an adversary. To understand what the conversation is really about.

Specific times and places are all well and good, but you said:

In various times and places better approaches to such situations have included: challenging the accuser to a duel, pressing a civil lawsuit for libel, public smear campaigns, Machiavellian political undermining or simple assassination.)

where the antecedent of "better" is "casual conversation" that "takes the form of questioning or the expectation of justification."

I won't speculate about what you meant by "better," but it sounds like a moral judgment to me.