"Who knew that taking history seriously could be so costly, or considered such a dangerous undertaking?"

Taking history seriously is always a dangerous enterprise when there are people who want certain truths ignored, swept under the rug, or forgotten.   Congar got into big trouble in the years preceding Vatican II.  Fortunately, the council called by St. John XXII rejected the fear dominated thinking of the pre-council years.  We are all richer because of Congar's work.