This is a really good question. It seems a non-disparagement clause waives one's right to the first amendment.
http://www.jaburgwilk.com/news-publications/what-is-a-non-di...
Is this right?
http://www.jaburgwilk.com/news-publications/what-is-a-non-di...
Is this right?
If they're legally binding then that's still bad.