In fact couldn't it be argued that admitting that there is an antidisparagement agreement is in fact disparagement because you acknowledge that something happened to cause said agreement to be entered into?
I don't think you'd easily win the argument, unless the parties involved generally didn't sign non-disparagement agreements.
I was once laid off from a company that gave me a small (but significant to me) severance check in exchange for signing a non-disparagement agreement. I did jokingly refer to that check as my "hush money", but I had no actual issue with the company or any of my former coworkers. That company did it simply as a matter of course, I imagine to make the laying off process more predictable.
(And I was pretty appreciative of the check itself; between it and my left over vacation days, I made it pretty comfortably to my next position.)
IANAL.