Imagine any other major change to your contract being implemented and the threat of sacking being the result if you do not agree.
You mean like the registrar who didn't want to officiate at same sex civil ceremonies.... and was sacked?
You mean like the massive changes to public sector pensions, which made them significantly less good, which nevertheless happened?
Change is inevitable. You can't go into a job and expect things never to change. And let's face it, NHS staff have had substantial notice that this was going to happen.
These are unprecedented times, we're living through a global pandemic and anyone bleating that 'they can't change my job' is being feeble. If you can't handle change in your life, be a hermit. Frankly, this is a pathetic argument.