Herbert Matthews bias showed in the 1930's when he covered the Spanish Civil War. He slanted his stories towards the Communist side. When a 100 year history of the New York Times was published the critics were acknowledged, but dismissed:
"Matthews had been labeled "Fascist" when he marched with Il Duce's Blackshirts in Ethiopia and now was blindly tagged "Red" because he reported from the Spanish Loyalist front. He was neither, but just a truthful and discerning reporter obeying assignment."
From the "The Story of the New York Times 1851-1951."
But his worst and most biased reporting was yet to come.
When the American Communists who fought in Spain during the 1930's held a reunion in the 1970's their invited guest was none other than Herbert L. Matthews.
An interesting review of the book.