For thirty-eight years I participated in hiring new faculty in a Univ. of California history department. For three years I was a member (and chairman for one year) of a faculty promotion committee on campus. I have some revelations to offer.
Faculty are recruited with advertisements and letters to people in relevant fields. The replies can be for a variety of academic and political positions in an academic field. The current preferences for fields, approaches, prejudices, and aversions (at least outside the hard sciences) invariably are somewhat skewed, depending on the discipline in question; the biases are not always political or even most of the time, but certain academic fields and sub-fields do involve political preferences. The preferences of those deciding on a short list of possible candidates become important.
What if some believe that certain ethnic origins result too often in certain academic prejudices? If enough people think so, good candidates may be left off a short list. On the other hand, some ethnic or religious origins are considered positive, and some candidates will be kept on short lists. Evaluating academic qualifications and accomplishments can often be a very inexact science in the humanities and some social sciences. This is my experience. Referees are not always unbiased.
I offer some true examples. What if one believes, for example, that ethnically Polish scholars cannot be sufficiently objective to teach Russian history? Or Muslim scholars to teach Israelite history? Or Catholics to teach the story of eastern Orthodox Christianity's history? Shall these beliefs be allowed to overcome obvious scholarly ability? Will one seek instead possibly equally good scholars who do not pose such perhaps real, perhaps imaginary problems?
I have encountered this. The more particular and narrow problem of American political preferences in the teaching of American history or politics or economics does exist. Existing department members tend to favor people with their own preferences or biases. Thus, departments get a particular coloration over time. This happens regularly. And while it is not desirable, it is very difficult to prevent. I do not suggest that one should therefore not try to prevent this. One should.