Even if laws against slander and libel appear good in theory, in practice they are all too often used by the powerful to silence the weak. A respect for free speech demands defamation laws be kept very weak.
The United States is not a nation. From the very beginning it was more of a collection of various nations united by ideas of political unity and by fairly high levels of tolerance for other groups within that union. The US certainly contains nations, but it was never a single nation.