I've been doing Reformation research for quite few years now. This is the best overview I've ever come across describing the mindset of Roman Catholicism toward the Reformers, and the Protestant apologetic needed to be employed against this mindset. It was written in 1856, and yet almost perfectly describes much of what I've seen over the last ten years of interacting with Rome's apologetic material against the Reformers, and likewise expresses some of the methodology I've used to respond.
The great general position which Romanists are anxious to establish by all they can collect against the Reformers, from their writings or their lives, from their sayings or their doings, is this, that it is very unlikely that God would employ such men in the accomplishment of any special work for the advancement of His gracious purposes. In dealing with this favourite allegation of Romanists, Protestants assert and undertake to prove the following positions:—1st, That the allegation is irrelevant to the real merits of the controversy between us and the Church of Rome, which can be determined only by the standard of the written word; 2d, That the allegation is untrue,—in other words, that there is nothing about the character of the Reformers as a whole which renders it in the least unlikely that God employed them in His own special gracious work; and, 3d, That the general principle on which the allegation is based can be applied in the way of retort, with far greater effect, to the Church of Rome. Protestants, by establishing these three positions, effectually dispose of the Romish allegation. It is with the second of them only that we have at present to do, and even on it we do not mean to enlarge.
Romanists have taken great pains to collect every expression from the writings of the Reformers, and to bring forward every incident in their lives, that may be fitted—especially when they are all presented nakedly and in combination—to produce an unfavourable impression as to their motives and actions. In the prosecution of this work, they are usually quite unscrupulous about the completeness of their quotations and the accuracy of their facts, and in this way they sometimes manage to make out, upon some particular points, what may appear to ignorant or prejudiced readers to be a good case. In dealing with the materials which papists have collected for depreciating the character of the Reformers, and thus establishing the improbability of God having employed them as His instruments in restoring divine truth, and in reforming the church, there are three steps in the process that ought to be attended to and discriminated, in order to our arriving at a just and fair conclusion:—
1st, We must carefully ascertain the true facts of the case as to any statement or action that may have been ascribed to them or to any one of them; and we will find, in not a few instances, that the allegations found in ordinary popish works on the subject are inaccurate, defective, or exaggerated,—that the quotation is garbled and mutilated, or may be explained and modified by the context,—or that the action is erroneously or unfairly represented in some of its features or accompanying circumstances.
2d, When the real facts of the case are once ascertained, the next step should be to form a fair and reasonable estimate of what they really involve or imply, taking into account, as justice demands, the natural character and tendencies of the men individually, the circumstances in which they were placed, the influences to which they were subjected, the temptations to which they were exposed, and the general impressions and ordinary standard on such subjects in the age and country in which they lived.
3d, There is a third step necessary in order to form a right estimate of the common popish charges against the Reformers, and of the soundness of the conclusion which they wish to deduce from them, viz., that we should not confine our attention to their blemishes and infirmities, real or alleged, greater or smaller, but take a general view of their whole character and proceedings, embracing, as far as we have materials, all that they felt, and said, and did, and endeavour in this way to form a fair estimate of what were their predominating desires, motives, and objects, of what it was that they had really at heart, and of what was the standard by a regard to which they strove to regulate their conduct.
A careful application of these obviously just and fair principles will easily dispose of the materials which papists have so assiduously collected for the purpose of injuring the character of the Reformers, and convince every intelligent and honest inquirer, that there is not one of the leading men among them who has not, with all his errors and infirmities, left behind him sufficient and satisfactory evidence, so far as men can judge of their fellowmen, that he had been born again' of the word of God through the belief of the truth, that he had honestly devoted himself to God's service, and that in what he did for the cause of the Reformation he was mainly influenced by a desire to promote the glory of God, to advance the prosperity of Christ's kingdom, and to secure the spiritual welfare of men.