A.A. Hodge offered this helpful advice when dealing with Roman Catholicism-
Dear friends, take my advice in this. In maintaining our evangelical position against Romanists, Ritualists and exclusive Churchmen, do not waste your force by laying emphasis upon any subordinate question as to church government, liturgies or parity of the clergy. Stand up only for essentials. Strike right at the heart of error.
The three central dangerous errors of Romanism and Ritualism are these:
(1) The perpetuity of the apostolate (which is the basis for the Papacy and Papal authority).
(2) the priestly character and offices of Christian ministers (the idea that human mediators are necessary to perform ongoing sacrifices or "mass" on behalf of the people).
(3) the sacramental principle, or the depending upon the sacraments as the essential, initial and ordinary channels of grace. (salvation is based in whole or in part on the grace transferred by the sacraments)
These are three radical heresies which exclude the truth, derogate from the honor of Christ and betray souls by inducing them to build upon false foundations. But if these three pestiferous roots of error are excluded, there can be no difference of radical importance between bodies of Christians who hold to the historic faith of "the holy catholic Church.