Relationships, be they personal, business, or otherwise, include dealbreakers. When a dealbreaker arises, there are two ways to handle it: unilaterally end the relation, or present it to the other party.

The latter is an ultimatum, there's no way around that. Whether or not the ultimatum is reasonable depends entirely on the specifics, especially in the workplace, employers have expectations which they need to have met.

It's especially distasteful to bake in the assumption that a romantic partner setting conditions to stay in a relationship is automatically being abusive. If someone is presented with an ultimatum to quit problem drinking or lose their partner, which is more likely: that the partner is abusive or that the other partner is an alcoholic? It's certainly not automatic that it's the former!

A policy of never meeting an ultimatum is one way to live your life, I prefer to consider whether the demands are reasonable and proceed on that basis. For me it shows a stronger sense of self worth to consider this kind of thing on the merits, rather than pre-committing to stick to my guns, which is in effect a counter-ultimatum. Sometimes that's the right move, sometimes it isn't.