This is not meant to exclude any other nutshell answers (if they’re accurate), but I have one that I think goes a long way to explaining what is happening.

B. B. Warfield once described Aurelius Augustine, Bishop of Hippo as a man whose Ecclesiology and Soteriology were in conflict. And he further described the Reformation as the triumph of Augustine’s soteriology over his ecclesiology. Finally, he defined the essence of Reformed orthodoxy as the confession that salvation was exclusively an immediate operation (no ecclesiology necessary) of the Spirit on the soul of an individual.

In the PCA, there are two kinds of people (highly inaccurate and yet a helpful model nonetheless):

1. Those who find in Warfield’s claims their very identity as Protestants.
2. Those who find Warfield’s claims to be both unfounded in logic (there is no necessary conflict) and in history (Neither John Calvin nor his heirs through the Westminster Assembly to Turrettin are Reformed Protestants by Warfield’s theological definition).

But here’s the problem: no one in the two groups actually thinks Augustine was right in everything he said either soteriologically (some think they do because the insist against history that Augustine was orthodox in his doctrine of justification) or ecclesiologically.

1. Thus, the impulse of group 1 is to continually accuse group 2 of beliefs they do not hold. Group 1 has two intellectual traps to fall into. They accept the “logic” that one must choose between Augustine’s soteriology and ecclesiology, so those who choose to remain in the broad form of his ecclesiology must reject his soteriology.
2. Members of group 1 assume a statement of appreciation for his ecclesiology means they can dig up any error of the past (“Romanist”) and freely apply it to members of group 2.

Thus, they are continually frustrated as particular facts are brought forth to show that the real world doesn’t match the world as they think it must be.

Guy Waters has written a book on the New Perspective in which he makes a foundational claim that backs up my analysis. Ultimately in religion there are only two destinies, Geneva or Rome.

Warfield marches on.