Questioning how these tweets came to be rediscovered is beside the point. They're there. They're his words. This is not in doubt and cannot be argued. And it wasn't a one-time lapse of judgment. It was dozens and dozens, over years- it was, in effect, his comedic style. Yes, they were from before he became known and somewhat of the time and he has since abandoned that comedic dead-end road.
But all of those factors seem to me to create a perfect opening for an apology that would probably be readily accepted- a disavowal of his past, making credible claims of having changed, a commitment to do better, something something. But he has not made one. His response has been since-deleted indignation, and then to purge his Twitter of everything but the most contemporary content (somewhat baffling, since folks know how to keep the receipts for this stuff).
The reaction and lack thereof speaks is... very telling.
"...everyone finally shut up, and the audience could enjoy the beginning of the Anatevka Pogram in peace."