From my own experience I found that my H tried to push my buttons to draw me into an argument (and I'm mind reading here) so that he could use it to add to his justifications as to why he left.
I actually believe they don't consciously do it to prove they are justified. I suspect they do it unconsciously, as part of their pattern and we react as part of the pattern, and thus reveals their justification.
So yes, by the LBS no longer reacting, they have nothing to push against and in that state of cognitive dissonance, their fear shows up as anger and they spew.
