I don't think anyone should ever be mean and bitter - in any situation.
I also agree that "paving the way" with a vanisher is a bit of a moot point.
I think where some of us are disagreeing is in the language about being "nice," "gracious," "kind" etc to the MLCer throughout.
Again, I don't believe we should be the opposite of those things: "mean," "bitter," "spiteful," etc.
But different situations call for different things. Some LBS can be kind and gracious and that's great.
But for some, being nice and kind in the face of cruelty doesn't feel right, and probably gives a wrong impression that the LBS will accept cruel behavior.
So perhaps instead of paving the way meaning "be kind and gracious," it should just mean, "don't instigate or engage in fighting" and rather than being kind to someone who is literally causing severe damage to your life, just be neutral. Don't vent your anger on them. Don't lecture them on what's right and wrong.
Protect yourself as much as you can financially. But don't feel you have to behave in ways that don't feel right to you. If your MLCer is being cruel and nasty, you don't have to say, "You're a good man and I love you." And you don't have to offer them coffee when they come by to pick up the kids. And you don't have to help them out of a jam they got themselves in. And you don't have to answer every call or text.
IF you're standing, you just have to take care of yourself and not be a constant fuming ball of anger. It's kind of as simple as that.
You don't have to make your MLCer view you as the nicest, kindest, most generous and forgiving person in the world (because they won't, no matter what you do). You just have to maintain your dignity in the face of a horrible situation (which will show them what maturity and strength is) and do what you need to do for yourself without doing anything to deliberately hurt/strike back at them and without an endless stream of nasty remarks and reminders of what they're doing and how wrong it is.
Just my two cents. If you want to pave the way, you can and should, but your needs (and those of your kids, if you have them) should still come first.
The desire to be loved is the last illusion. Give it up and you shall be free. ~ Margaret Atwood