If the policy 'don't speak ill of the dead' was universally applied, subsequent generations would never be told of the deeds of Hitler, Stalin and Mussolini.
Incidentally, my italian ex mother in law was eternally grateful to Mussolini because he financed surgery for her as a child - not a relative - just human compassion.
No one is 100% good - knowing their failings as well as their good deeds provides a balanced view of a personality.