Jeffrey Sachs (not the economist) asks, Why are psychologists so prevalent in the free speech movement?:
If any academic field is associated with the contemporary debate surrounding free speech, it’s psychology. Haidt, Pinker, Peterson, Saad, Jussim, even Lehmann. All specialize or have backgrounds in academic psych.
The Scholar’s Stage offers a good answer:
I attribute this all to three things.
1. The conclusions academics reach tend to rankle the right. There are exceptions. If your research draws on evolutionary psychology, focuses on innate behavioral differences, or touches any sort of psychometrics (e.g., IQ), the angry tide does not sweep in from the right. The wave these men and women fear crashes in from leftward side. Moreover, the sort of leftist opposition that the academic consensus on these topics face leaves little room for rational debate or compromise: controversies over psychometrics or evolutionary psychology are usually framed in terms of good and evil, not right and wrong. The scientists involved are to be conquered, not reasoned with.
So that is point one: the people who want to shut controversial psychologists up are overwhelmingly creatures of the left.
2. Psychology, especially social psychology, is itself an overwhelmingly leftist discipline. We actually have data on this, and it is pretty grim: a recent survey of American tenure-track professors reveals that there 17.4 registered Democrat psychologists for every single registered Republican. If there is a field of people who ought to be sympathetic to social justice railroading, these people are it.
3. Despite this, behavioral scientists have not yet adopted the rhetorical techniques or methodology of inquiry of “critical theory.” In contrast, see how these modes of inquiry have swallowed up the fields of anthropology and communications, and established creeping colonies in history, sociology, and area studies. Given the left-leaning sympathies of almost all in the profession, the threat that the same might happen to the study of human behavior is real.
…Haidt et. al. are confident they can win the debate if they are allowed to debate. For the heterodox anthropologist or sociologist the game is already over: their discipline has already been conquered. For the economist, the threat is too remote to take seriously. Behavioral science exists in that rare in-between: methodologically, it has the tools to fight back against the excesses of the activist. Socially, it provides a compelling reason for its practitioners to use them.