For those who haven’t followed the immigration debate closely over the years, the screed posted online minutes before the El Paso shooter opened fire at a Walmart, killing 22 people—mostly Hispanics— might have seemed an odd mix of right-wing hate and left-wing environmentalism. On the one hand, the writer said his attack was a response to the “Hispanic invasion of Texas,” while at the same time decrying “the decimation of the environment” and overpopulation. But those same tropes are familiar to those who have spent time fighting groups like the Federation for American Immigration Reform (FAIR), the Center for Immigration Studies (CIS), and NumbersUSA, as I have for more than 30 years.

Decades before Donald Trump cast his first aspersions against Mexicans as “rapists,” John Tanton, the founder of all three of these groups warned that Hispanic immigration was going to lead to “the first instance in which those with their pants up are going to get caught by those with their pants down!” Tanton, who died in July, was obsessed with three interrelated issues: immigration, population growth, and the demographic shift taking place in the United States.

I first met Tanton, an ophthalmologist from Petosky, Michigan, in 1987 when he offered me the job of president of USEnglish, a group he started with former Senator S.I. Hayakawa (R-California), which operated under the same tax-exempt umbrella, U.S. Inc., as FAIR, CIS, and NumbersUSA. USEnglish’s mission was to pass a constitutional amendment to make English the nation’s official language. I have long believed that having a common language has been one of the key reasons why the United States has succeeded in integrating immigrants successfully into the American mainstream. A constitutional amendment to declare English the official language seemed to me mostly symbolic, but unobjectionable, so long as it was understood that individuals were free to speak whatever language they chose in their families, churches, synagogues, and community organizations. My chief concern at the time was that public schools were no longer trying to teach newcomers English quickly but were relegating immigrant children—and even those born in the United States—to so-called “bilingual education” classes, whose main purpose was to maintain the child’s mother tongue.

I told Tanton that I hoped to steer the organization to take on the bilingual education lobby and to promote English immersion lessons as a more effective method to help newcomers learn the language that would be the key to their educational, economic and social advancement. During my tenure the organization developed classes for new immigrants to learn English in their workplaces and made available to immigrant groups a series of videotapes that taught practical English-language skills for opening bank accounts, applying for jobs, and coping in their new communities. Because USEnglish was a cash cow for Tanton’s U.S. Inc., raising far more money (mostly through direct mail solicitation) than any of his anti-immigration groups , Tanton was willing to ignore my frequent pro-immigration opinion columns and largely left me alone to run the day-to-day operation as I chose. But the relationship ended less than a year later when I discovered Tanton’s racist memo, written before I joined the organization. When I resigned, so did a number of high-profile figures who had served on the advisory board of USEnglish, including Walter Cronkite, Arnold Schwarzenegger, and Jacques Barzun, and USEnglish eventually split off from Tanton’s U.S. Inc.

Tanton began his public policy career in the population control and environmental movements. Before founding U.S. Inc., he was national president of Zero Population Growth in the mid-1970s and on the executive board of the Sierra Club. He founded FAIR in 1979 when he decided that the only way to stop population growth was to limit immigration, especially immigration of Catholics. His infamous memo warned of higher birth rates among Hispanics, which he attributed in part to Catholic opposition to birth control; “Can homo contraceptivus compete with homo progenitiva if borders aren’t controlled?” he asked in pompous Latinate phrasing. And he also claimed the Catholic Church would threaten the separation of church and state: “The Catholic Church has never been reticent on this point. If they get a majority of the voters, will they pitch out this concept?” In 1985, Tanton created CIS as a separate think tank to promote advocacy research on immigration topics. In 1997, a man named Roy Beck founded NumbersUSA under the auspices of Tanton’s tax exempt umbrella, though the group spun off in 2002.* All of the groups combined Tanton’s fixation on population and the environment as part of their overall immigration agenda. Admitting immigrants increased the size of the U.S. population by definition, but it also contributed to population growth when the immigrants came from countries with higher fertility rates—and more people meant more pollution and environmental degradation, according to this line of thought. FAIR, CIS, and NumbersUSA over the years have attempted to link immigration to water shortages, traffic gridlock, increases in greenhouse gases, urban sprawl, and other environmental issues. But the groups haven’t stopped there. Not only Tanton but other prominent figures in the organizations have promoted mass sterilizations in Africa, embraced eugenics, endorsed forced contraception and abortion, and euthanasia, as I and others have written about at length.

By all means Donald Trump deserves blame for the pernicious effect of his anti-immigrant rhetoric in fueling attacks on immigrants. But when Trump speaks of Hispanic immigrants as invaders and describes them as “infesting” our nation, he has company in the corners of the immigration restriction movement that regard immigrants as pollutants of our environment and our culture. The El Paso shooter’s ideas on immigration, cultural replacement, and the environment weren’t original—many of them can be found hidden in plain sight on supposedly mainstream immigration restriction organization websites, in best-selling books by conservative authors (Ann Coulter, Michelle Malkin, Mark Levin, among others), on talk radio and cable news. I have been warning for years as a conservative that we have a special burden to ensure that we reject racism, and that the rhetoric surrounding immigration often crossed the line. In 2007, I wrote in a long article for National Review Online that words matter, and some of the most provocative have come in the pages of National Review. I warned then that it would be “dangerous to win the immigration debate by stirring up racial or ethnic animosities by playing to the prejudices of that small group of Americans who are motivated by racism and nativism.” Unfortunately, the admonition went unheeded—and the consequences can be seen as El Paso buries its dead.

Clarification, August 12: The article has been amended to say that NumbersUSA was founded by Roy Beck and that it split from U.S. Inc.