The day before the inauguration of Donald Trump, whose anti-immigrant campaign garnered him nationwide support, Twitter has allowed the Federation for American Immigration Reform (FAIR), a known hate group, to promote its #StopSanctuaryCities hashtag with a paid advertisement on the popular social media site.

On Twitter Thursday, the group is pushing its anti-immigrant agenda using the hashtag #StopSanctuaryCities, intended to “pressure President-Elect Trump & Congress to start enforcing our immigration laws.”

FAIR promotes itself as a “non-partisan” organization that “seeks to improve border security, to stop illegal immigration, and to promote immigration levels consistent with the national interest.” However, as the Southern Poverty Law Center (SPLC) noted on its website, the group’s leaders have ties to eugenics and white supremacist groups. FAIR’s founder, the racist, nativist, John Tanton, “has expressed his wish that America remain a majority-white population: a goal to be achieved, presumably, by limiting the number of nonwhites who enter the country,” according to the SPLC.

On the campaign trail, Trump cited FAIR’s false and misleading anti-immigrant reports often, relying heavily on the group’s assertion that more deportations would reduce crime in the United States.

As Rewire reported, during Trump’s highly-anticipated speech on immigration in Phoenix, Arizona in September, he promised to block federal funding for so-called sanctuary cities—a term for those that have vowed not to criminalize undocumented immigrants based on citizenship status alone.

“Block funding for sanctuary cities … no more funds,” Trump said in Phoenix. “Cities that refuse to cooperate with federal authorities will not receive taxpayer dollars, and we will work with Congress to pass legislation to protect those jurisdictions that do assist federal authorities.”

As Trump prepares to take office, mayors from across the country have stepped forward to reassure undocumented immigrants that they are safe in their cities. However, Republican lawmakers, emboldened by Trump, continue pushing to punish cities participating in the sanctuary movement, with the ultimate goal of barring sanctuary cities entirely.

Antonio Arellano, an advocate and multimedia journalist, was one of the first to point out that Twitter was running an ad from a prominent hate group, something he says left him in “absolute shock” this morning.

“By running this ad, Twitter is sending a very strong message of discrimination against many of its undocumented users living in the states. No amount of advertising money can cover the cost of racism,” Arellano told Rewire. “I think it’s absolutely shameful that a social media platform would promote, allow, or approve paid ads from a designated hate group, especially in this political climate the day before the inauguration.”

Arellano told Rewire in a phone interview that Twitter is being irresponsible by allowing FAIR to promote its anti-immigrant agenda, and that being irresponsible can put people’s lives in jeopardy. He recently participated in the #HereToStay hashtag, created by leading immigrant and labor rights organizations in honor of a national day of action to tell President-elect Trump that immigrants are a permanent and important part of the United States. Arellano said he received abuse on Twitter for participating in the hashtag, and that doing a basic search of the hashtag revealed anti-immigrant Twitter users targeting immigrants like Arellano with thinly veiled threats. Users such as Steven Hirsch, who tweeted, “If you’re illegal, using the hashtag #HeretoStay only makes you easier to find. Keep it up!! You’re doing great! Trust me, we’re watching.”

“It’s very dangerous to allow organizations that have large followings, like FAIR, to pay for advertisements on Twitter when they are actively pursuing actions that put people’s lives in danger. Look at the tweets using FAIR’s hashtag about sanctuary cities. When people are making immediate threats using a hashtag, it needs to be taken seriously. Using this type of rhetoric against people is inappropriate and should be condemned,” Arellano said.

In recent years, Twitter has become more known for allowing abuse than promoting dialogue. This isn’t the first time the site has come under fire for its advertising policies. In 2014, the social media site blocked condom companies and sexual health campaigns from advertising about condoms and safer sex. Why the company would take issue with a sexual health message but not, apparently, with an ad from a designated hate group promoting its anti-immigrant agenda remains unclear, as Twitter did not respond to Rewire’s request for comment.

“As more activists are targeted on Twitter, sometimes because of ads or because of Twitter’s failure to combat abuse, I think Twitter needs to be more transparent regarding its advertising policy,” Arellano said. “How is it OK to promote ads saying we need to stop sanctuary cities, but not ads that promote safe sex? We need to get to the core of who makes these decisions at Twitter and hold them accountable.”