The main point I want to make is that ultimatums are a very dangerous business - there's a risk that people will find out that you're not really capable of carrying out your threats, and that you're just bluffing. And if people ever figure that out about you, you are seriously screwed, with a capital-"S".
Fortunately, I think that people who are absolutely rigid and unwilling to compromise are, for all practical purposes, non-existent - the vast majority of people will accept some sort of compromise, so the issue then is hammering out a compromise that acceptable to everyone. Maybe there isn't one, in which case, the divorce might as well come sooner rather than later. I suspect there is one lurking in there somewhere, though, but the first step to getting there is in realizing that if the libs get in, we all lose, and that while getting everything you want is best of all, getting something is better than getting nothing. People who demand the whole loaf or nothing at all have a habit of starving, essentially.