Some comments.
First off in 1939 what had transpired was not yet the Holocaust but the removal of civil liberties from Jewish people. One needs to remember that a feature of Administrative Law since it began, including the French Revolution which was a very different affair than the American, is that civil rights as only being political in nature can be revoked just as easily as they are given. The NYTs would have been unable to loudly protest the natural result of Administrative Law because as so-called “progressives” they were among those laboring to push that form of laws on America.
You may also note that at the Nuremberg Trials they likewise did not ever, even for a moment, suggest that the Administrative Law form was inherently bad and dangerous, instead inventing an ex post facto offense, crimes against humanity, to charge Germans etc with. Those proceedings could be said to be covering up 1939 too for that cause.
Now, as for the Left covering up the horrors of the Soviet Union I would point out that this was far from a single example. We learned not too many years ago that the supposed truth teller, Upton Sinclair, outright knew that Sacco and Vanzetti were guilty but wrote Boston as an exoneration because it would sell well with his Leftist readers in Europe. Lying to cover up what the Left does is just what the Left does. It’s why even at this day they are upset because Trump supposedly threatened to get an investigation reopened BUT are not even a bit upset that Biden threatened in order to get said investigation shut down.
It’s also worth noting that among the Nuremberg judges were Stalinist apparatchiks who had to be instructed by the Americans as to how to simulate jurisprudential proceedings because they only knew how to administer show trials against “counterrevolutionary wreckers” and “capitalists.”