Fox News commentator Juan Williams thinks he understands the reason for his firing by NPR: The radio news organization's management was "antagonistic" toward Fox and "vindictive" about his appearances on the cable news channel, he says.

Appearing on ABC's "Good Morning America," Williams told host George Stephanopoulos: "I knew about [NPR's] antagonism towards Fox. I knew they really didn't like it. As I said, I've been there more than 10 years. I've seen managers come and go and who dealt with this issue. This current crew was really getting vicious. And as I say, [it was] personal, in terms of their animus. I had a sense that they were really looking for something."

Williams, 56, was fired late Wednesday after saying on Fox News Channel's "The O'Reilly Factor" on Monday that he was "nervous" being on a flight with people in "Muslim garb." Williams denied that his statements were bigoted, but NPR decided that it had had enough of Williams's commentaries on Fox and terminated his contract as an NPR analyst.

NPR officials say that the issue is a long-standing one and that Williams had been warned not to engage in personal commentary on controversial issues, both on Fox or on NPR, where Williams is most often heard on its "Weekend Edition" program as a news analyst. Washington-based NPR has said Williams's doing so undermines its credibility as a news organization.

Dana Davis Rehm, a spokeswoman for NPR, said that Williams's repeated violations of NPR policy sparked the dismissal and that it was unrelated to the fact that Fox hosts, such as Glenn Beck, Sean Hannity and O'Reilly, often express conservative opinions.

NPR hired Williams in 2000, after he had been on Fox News for three years. Mara Liasson, a veteran NPR reporter, has been a Fox News contributor for years while simultaneously serving as an NPR reporter. Liasson, however, appears on Fox news-discussion programs, not the more volatile and often emotional prime-time talk shows on which Williams often appears.

On ABC, Williams said the issue had become "personal" after NPR President Vivian Schiller told an audience in Atlanta on Thursday that Williams should have kept his comments between "himself and his psychiatrist." Schiller later apologized for the remark, although Williams said she did not apologize directly to him.

"I don't know why she has to get that low," he said. "She has an argument to make that I somehow violated journalistic ethics or values of NPR, make the case. I think it's a very weak case. Ultimately, what she had to do then was to make an ad hominem, more personal attack."

He added: "Am I unstable or irrational? . . . If I was such an erratic character, I think this would have come to the fore long ago."

He repeated comments made to The Washington Post on Thursday that NPR selectively edited his statements about Muslims.

"They take one statement, and they somehow make it out that I am a bigot," he said on "GMA." "It's unbelievable to me, given the books I've written, the things I've done in my life. Now all of a sudden, I'm a bigot? All I said to Bill O'Reilly is we have to be careful about kind of the language and things we say in the public. . . . I was saying that we have to protect the rights of Muslims in this country."

Williams said NPR's reaction to his comments was "a shock," given that he believed that the organization, often described by conservative critics as liberal, was more tolerant of contrary opinions than conservatives.

"I've always thought the right wing was the ones who were inflexible and intolerant. Now, I'm coming to realize that the orthodoxy at NPR, if it's representing the left, is just unbelievable. And especially for me as a black man, to somehow, you know, say something that's out of the box. They find it very difficult. . . . I think they were looking for a reason to get rid of me. They were uncomfortable with the idea that I was talking to the likes of Bill O'Reilly or Sean Hannity."