Prescribing ban is ethically dangerous
You clearly find it irksome as the senior partner to be in a minority to these zealous new partners, but you need to find a way past this. Your greater experience can win the day.
The food issue is easiest to tackle. It is likely the large majority of your staff are not vegan. The new partners are now employers and as such it is unfair to deny staff use of the fridge and microwave for meat products. Your partners have no choice but to think again about this.
The prescribing proposal is both ethically and practically dangerous. If a patient's medical condition requires a drug on your partners' banned list, there will not always be a medically acceptable alternative.
What will your partners do then? If they pursue this path, sooner or later a patient's health will be put at risk and they will be liable for the consequences. Write to your defence body to ask its opinion and show your partners the reply. This is certain to back you up. Advise your partners what you are doing and decline to join their proposal. This is a personal not a practice issue.
Returning to the food problem, if your partners' beliefs are so strict that vegan food cannot share space with non-vegan then the solution is a second microwave and refrigerator.
· Sooner or later a patient's life will be put at risk and your partners would be liable