There's nothing wrong with one side or the other asking for a negotiation or renegotiation in good faith. Contracts are not immutable, they get amended all the time for all sorts of reasons.
Choosing to withhold your labor until a renegotiation happens is an extreme tactic that is likely to generate bad faith from the other party long term, but it's always legal and always moral because our society considers slavery unacceptable.
Contracts are an important part of working conditions, as are workers perceptions of self-worth. If your contractual working conditions are demeaning such that you're prepared to not get paid and potentially risk being terminated in order to protest the demeaning conditions, no reasonable person would attempt to force you to work.
It is to the companies benefit in these cases that knowledgeable employees attempt to solve the problem rather than simply leaving. It is much cheaper to amend contracts than train new workers. This is a classic case where amending relevant contracts benefits everyone.
Is that does that help you straighten this out?