THey know the libel laws make it nearly impossible for anyone to win a lawsuit, because it’s nearly impossible to prove that they acted out of malice. But in this case a suit would be more of a political statement, defusing the argument to some extent, and while the NYT will never print a retraction, it could tamp down some of the emotions, because to NOT sue sends the message that he is guilty.
He can always drop the suit later.
FWIW, "actual malice" in defamation law has NOTHING to do with ill will.