When Texas lieutenant governor Dan Patrick declared earlier this year that he would remove tenure protections so that a “handful of professors” can no longer “indoctrinate students with critical race theory”, he was unwittingly repeating rhetoric from the unsuccessful side of a 100-year-old culture war. Across the United States, there at least 49 active bills that would crush the freedom to learn and teach on university campuses — 25 of the 50 states have at least one.

As a historian, I’ve studied the battles over education in the United States. Although fights for control of universities are waged on the fields of science, literature and history, they are won with different sorts of argument.

Critical race theory (CRT) emerged in the 1970s as a legal analysis of racism deeply embedded in society. Warnings against CRT are new, but the arguments mirror a 1920s-era assault on teaching evolution in US universities. Conservatives then, as now, sought to ban teaching of an accepted theory that threatened their world view.

In May 1921, the University of Wisconsin in Madison hosted an anti-evolution lecture by popular pundit William Jennings Bryan — who later became famous for arguing in the Scopes monkey trial in Tennessee, about teaching evolution to schoolchildren. University president Edward Birge, a prominent zoologist, criticized Bryan’s speech and drew national conservative fury.

Bryan demanded that Wisconsin’s instructors stop teaching evolution, and that Birge personally affirm a belief in creation as described in the biblical Book of Genesis. Otherwise, Bryan said, a sign should be posted at the entrance to campus describing its classrooms as “an arena in which a brutish doctrine tears to pieces the religious faith of young men and young women”.

Meanwhile, another campaign took aim at Howard Odum, a professor at the University of North Carolina in Chapel Hill and editor of a peer-reviewed journal, which had published two articles critical of the historical truth of Christian miracles. Conservatives called for Odum to be fired or reprimanded and for the university to support only research that affirmed Christian doctrine. In Greensboro, North Carolina, another instructor, Albert Keister, described evolutionary theory as a powerful scientific tool and accounts of six-day creation as “a form of mythology.” This fuelled calls for a state-wide law to ban teaching of evolutionary theory at public colleges and universities. Harry Chase, the president of the University of North Carolina, managed to defeat the proposed legislation.

How? He did not engage in debates about evolutionary theory. He did not rebut (absurd) charges that only atheists could embrace modern science, nor address distinctions between religion and mythology. Instead, he argued that a law banning the teaching of evolution would spell the death of any “real university”, and that attacking the “quality of faculty” would undermine high-quality education. Faculty members, students and administrators were able to organize and mobilize a broad mass of popular support that had been relatively quiescent. Support for the restrictive bill turned out to be a paper tiger.

In Wisconsin, Birge took a similar stance. Instead of taking on Bryan’s arguments that evolutionary theory was weak or that learning science turned people into atheists, Birge argued in favour of academic prestige. If Wisconsin wanted a high-quality university, it must accept academic freedom. He recruited prominent faculty members across disciplines to back him. He publicized the demands of tax-paying Wisconsinites who decried an “expurgated education” and successfully defended his university.

Today’s push for conservative control of universities is just as ambitious. Moreover, today’s scholars are more vulnerable: higher-education budgets are depleted, and some university departments and programmes are simply being eliminated, not just criticized. The situation in the United States is exacerbated because higher education is decentralized and so more vulnerable to pressure from local zealots. Yet that broad support remains powerful. However, just like in the 1920s, tapping into it requires clear-sighted leadership by professors and administrators.

Jay Hartzell, the current president of the University of Texas at Austin, repeated the 1920s defence almost verbatim, saying that the proposed legislation would “cripple Texas’s ability to recruit and retain great faculty members”.

The fact that this tack worked before is no reason to be complacent. Just like in the 1920s, today’s threats to academic freedom are severe and will require staunch activism to defeat. Yet even politicians who campaign against what can be taught in children’s schools still want universities that attract prestige and research funds. The support comes from influential big-business organizations as well as tech leaders, university-attending families, and even state pride.

It might be tempting for scholars and university presidents to enter into point-by-point refutations of conservative charges or make technical arguments about whether lectures on history or science are actually critical race theory (or other conservative bogies).

Those attempts have never worked. Facts alone — no matter how well-grounded — have never been able to defeat determined assaults on intellectual freedom at research universities. Instead, made forcefully, broadly and fully, arguments about quality have prevailed.