You're arguing negative reciprocity is limited to same same here, that escalation is unjustified, which ignores that in the first place in order to have that reciprocity you must have an initial escalation. Focusing solely upon the act of stacking as the escalation, leading to further one upmanship, while completely ignoring that it is the actions of the GOP here that are the initial escalation, makes no sense.
The Dem's choice is to be rolled, or retaliate. Personally if I was in their position, given the opportunity, I'd go nuclear.