In Imus' case, CBS was the guilty party. IMO, Dog has a lucrative lawsuit here.
I'm betting just about every contract involving an entertainer has some sort of vague, boilerplate language about reflecting negatively on the show or network, moral turpitude, etc. That kind of stuff.
Whether his conduct was illegal or not makes zero difference.
If his son had gone to the media and reported that Dog used the N-word then nothing would have happened.
However, the conversation is no longer private when it is taped and broadcast on the Net and TV. And yes, the Dog should have understood that he may have been being taped.
And now, his former employer and everyone in the country knows that the Dog is a moron.
The Dog does not have a case against A&E.