What do you do with a spouse who mostly respects your boundaries but is boundaryless themselves and resort to ultimatums and threats?
You learn the fine DB art of "I'm sorry you feel that way," and you tell them to "do what you feel you have to do," and you -- as someone noted above -- instead do "The Right Thing to Do."
It also depends on what their stated consequences are, and what your options are -- Strengths, Weaknesses, Opportunities and Threats (the classic business "SWOT" exercise). Some hands you hold are stronger than others, and sometimes you have to acquiesce to even a poorly-stated ultimatum, if your options are less than desireable.
