Worth noting: Ailes has yet to apologize to NPR itself — and it doesn't sound like he has any plans to.
Here's part of the letter he sent to Anti-Defamation League National Director Abe Foxman (via TVNewser):
This morning you might be receiving calls because I used the word ‘Nazi attitudes’ to describe the NPR officials who fired Juan Williams. I was of course ad-libbing and should not have chosen that word, but I was angry at the time because of NPR’s willingness to censor Juan Williams for not being liberal enough.
I’m writing this just to let you know some background but also to apologize for using ‘Nazi’ when in my now considered opinion, ‘nasty, inflexible bigot’ would have worked better. Juan Williams is a good man and I like you as a friend. And my friends never have to worry about me sticking up for them — even if I’m occasionally politically incorrect I never leave any doubts about my loyalty.
Foxman issued a release accepting Ailes’ apology. “I welcome Roger Ailes apology, which is as sincere as it is heartfelt,” Foxman, a Holocaust survivor, said in a statement. “Nazi comparisons of this nature are clearly inappropriate and offensive. While I wish Roger had never invoked that terminology, I appreciate his efforts to immediately reach out and to retract his words before they did any further harm.”