The first part is totally reasonable. If the company wants to change policies and you don't agree to those policies (and are in no way able to change them), why should they let you stay? Why should you let yourself stay? If a new policy is that egregious that you would rather possibly lose your job than sign in agreement, why would you even want to stay there? At that point, it's in everyone's best interests to part ways before it becomes a real issue.

If the company actually cares about keeping you and they have any sort of leeway as to changing the policy, they will listen to why you can't agree to it.