Here’s a related question: How should we feel about Catholics who like to be familiar with Protestant theology? In a way that’s an even more pressing problem. I have to get along well with my fellow Catholics, and I always cringe inwardly when they happily chirp about Calvinist this or Lutheran that… It isn’t that I assume that they agree with the Protestant theology, but they’re so chirpy that I cannot be sure that they really appreciate the need to embrace Catholic theology. I worry that they may be blending theologies simply because they feel that it would be a nifty thing to do. I don’t necessarily trust their ability to tell what is true and what is misleading.
I think the best reason not to study Protestant theology, at least at first and for a long time, is that one may not be prepared to spot the problems. When bank personnel are prepared to spot forgeries, they attend a ten-day course. For the first nine days, they spend all day, each day, counting legitimate notes. On the last day, false notes are slipped into the stacks. Only late in the course, in other words, are problem notes given as examples.
But, as long as one can keep oneself straight, chirpy fellow Catholics aside, it is important to be familiar with where different branches of Protestantism err. Even more than that, however, we must recall that individual Protestants probably don’t know their own theology all that well, and will tend to fall not so much to the peculiar errors of their sect, but to the more general problems of relativism, modernism, not believing in palpable guiding authority, etc.