Protestants should embrace, study and love all of the pre-Reformation Christian writers as their own, especially the universal and common doctor!
"...I believe that the testimony of the 'universal teacher' of a still undivided Western Christianity has a special value. This lies not so much in his personal genius as in the truly creative selflessness with which he expressed the vast, contrapuntal range of possible statements about the cosmos--even as he recognized and called upon his readers to go beyond the limitations of his own vision. Marked though this thought is by an altogether extraordinary grasp and the most disciplined, dynamic, and penetrating independent thinking, there yet speaks through it less the individual writer, Thomas Aquinas, than the voice of the great tradition of human wisdom itself."
Joseph Pieper, The Four Cardinal Virtues, Notre Dame, University of Notre Dame Press, 2006, preface, xii-xiii.
Consider in this regard the position of Saint Bridget, the patroness of Sweden or Saint Thomas A' Becket and Saint Edward the Confessor in England. Why should not Saint Thomas Aquinas and Saint Albert the Great have at least equal veneration by the Protestant German! They are all part of the rich Christian patrimony of us all. That's ecumenism! Protestants need to cherish their true Christian heritage, which is mainly Catholic (i.e. universal and common to all places and times)!
How can you cherish Chaucer's Canterbury Tales and despise the Saint of Canterbury to whose Shrine the pilgrims progress? It is our common Christian patrimony, which cannot be despised, rejected, ignored or neglected, without great damage to ourselves.
An educated Protestant who has never read Saint Thomas Aquinas is an oxymoron, for he is ignorant of a heritage which is, in fact, his own. It's like a man who does not know who his own mother is.
This is a case similar to that of Saint Francis. There is absolutely no way a Protestant can have a problem with the Christianity of Saint Francis of Assisi. Why should he reject the school men? who were exactly the same type of Christians as Saint Francis.