Been there done that. I've been in your spot and your boss's. If I were in
your place right now I would just toss the thing in the trash. They sure as
hell aren't going to fire you for not signing it. The whole purpose of the
thing is to intimidate you into not taking a better offer. My guess is that
some of your cohorts have gotten calls from headhunters (ask around) and
management is trying to avoid a bidding war. It's an old trick