Every generation of scholars creates its own interpretations of the past.It is hard to tell what the real issue is, because it does not cite or link to whomever it is criticizing.
Reading between the lines, it appears that nearly everyone who seriously studies Medieval history comes to the following conclusions:
1. 3000 years ago, the most advanced civilizations were in Middle East, Persia, India, and China. Europe was lagging.
2. During Europe's so-called Dark Ages, it built a civilazation that was to leap frog far ahead of those outside Europe.
3. The primary ingredients for success were White people and culture, Christianity, and a willingness to fight for their beliefs.
4. The success was not based on any technology, natural resources, or conquests.
5. The Crusades and related battles kept Moslems and Jews from taking over Europe, as they would have ruined it.
If these conclusions are wrong, then I expect that the politically-correct Medievalists would try to rebut it. Instead they just say that they are free to create their own interpretations and things like this:
Scholars disagree about the motivations of the Crusades — or, indeed, whether the idea of “crusade” is a medieval one or came later — but it is clear that racial purity was not primary among them.Sure, the Crusades were more about religious purity than racial purity.
White Christian Europe achieved greatness in the last 500 years, while the Islamic world declined. Various explanations have been given. I do not know which is best, but I am pretty sure I won't get it for those 29 Medievalist societies. They have already said that they oppose discussing scholarship that "hurts people in the present". I am pretty sure that any good explanation will cause bigotry complaints.