In March 1937, the State Department apologized on behalf of the United States to Adolf Hitler for comments made about him by the Mayor of New York City, Fiorello LaGuardia.
"In this country the right of freedom of speech is guaranteed by the constitution to every citizen and is cherished as a part of the national heritage," James C. Dunn of the State Department said. "This however does not lessen the regret of the government when utterances either by private citizens or by public officials speaking in an individual capacity give offense to a government with which we have official relations. I very earnestly deprecate the utterances which have thus given offense to the German government. They do not represent the attitude of this government toward the German government."
75 years later the great tradition of American diplomats apologizing to mass murderers for the American tradition of freedom of speech remains alive and well.