I found this quote from Fr. Louis Bouyer from his book Protestant and Anglican Spirituality, which is part of his 3 volume set, A History of Christian Spirituality, (New York: Seabury, 1962-1964).
I like it and I agree with the sentiment in it. Please note that this was written before Vatican II by a Catholic theologian of impeccable orthodoxy.
What holy souls Protestantism has produced among its great spiritual exponents, and what admirable teaching of the most genuinely Christian kind! And, let us say it again, the spiritual principles enunciated by Luther and Calvin were, and still are, the initial driving-force of their whole quest for God in Christ, Yet the quest was successful precisely in so far as it separated these principles from all the non-biblical elements that the reformers themselves had attached to them, and which had made the Reformation schismatic and heretical.
The conclusion of all this is undoubtedly that Protestants belong to the Catholic Church by what is best in them, and that what is most rightfully dear to them can only flourish in a certain and lasting way in her bosom, while the split between Orthodoxy and Catholicism is a misunderstanding, an absurd and scandalous nonsense.
But this is only half the truth. We must now add all the things that the Catholic Church has lost by the loss of the Orthodox and the Protestants, and all that Catholics still need to do to be reunited with them in the one Church.
There is a sense in which no division can cause the Church to lose anything that is essential to it. The separation between East and West does not prevent the Greek Fathers, nor the Eastern liturgies, nor the treasures of thought and spirituality accumulated by the Byzantine tradition and its heirs, from belonging forever to the Catholic Church. And even the ruptures involved in the Protestant Reformation could do nothing to prevent the Word of God from being the great and incomparable richness of the whole Catholic tradition, or salvation from being for every Christian a grace that faith alone can grasp, or faith from being the starting point of the most intensely personal relation of each soul with God in Christ. Whatever the schisms and heresies, every Christian in the Catholic Church can go on drawing life from all that…
How different the spirit and tenor of this gentle priest’s assessment from what we see too often in places like this.