One of my favorite stories involves Stalinologist Robert Conquest. In 1968, Conquest wrote a detailed history (The Great Terror) of the Stalin purges of the 1930s demonstrating the mass murders and terror state that Stalin created based on the sources available. Conquest was pilloried by academia. In the early 1990s, Russia made available KGB/OGPU/NKVD documents from the Soviet era and other government information -- more than 2,000,000 pages of stuff. Conquest used it to update The Great Terror, and the information not only confirmed the thesis of his book, but showed that he understated the death count and the situation. When asked by his publisher what he would use for a new title, Conquest said, "how about I Told You So, You F*cking Fools?"
[N.B. -- I edited Conquest's quote, he didn't self-censor]
Left-wing academics and apologia for Communism go hand in hand, even today after the USSR files have been accessible for more than a decade. A great analysis and take-down is in the book, In Denial: Historians, Communism and Espionage, by John Earl Haynes and Harvey Klehr, which is discussed here in a great article.