An ad currently rotating on video screens at two downtown San Francisco BART stations will appear through month’s end, in spite of the agency’s desire not to air it.

The ad, which reads “History matters,” began running on Labor Day at the Powell and Montgomery stations. It’s sponsored by the Institute for Historical Review, which the Southern Poverty Law Center has classified as a hate group that seeks to promote revisionist narratives downplaying and distorting the Holocaust and other events.

“We cannot deny the ads,” BART spokeswoman Alicia Trost told The Guardian on Tuesday.

“You have to look at it for exactly what words are used and what images are used. … There is plenty of case law and court rulings that show if you deny the ad, you can be taken to court, and you’ll lose, and that’s obviously costly.”

Trost told this news organization that the group paid $6,000 for the ad, which she said is really not that much.

“Riders are smart, and they’ll probably be upset when they find out who’s behind the ads,” she said. “Would they know that just looking at the ads and without this being blown up in the media?”

Transit systems across the country have faced similar difficulties over challenging advocacy ad campaigns.

This spring, BART aired ads by an organization seeking to limit what it called “unintended consequences of mass migration.” The transit agency took pains to make clear it did not endorse the ads.

“The campaign complies with free speech laws that allow advertisers to express a point of view without regard to the viewpoint. BART must post these ads to comply with the law,” the transit agency said in March. “Court rulings reinforce the fact that we can’t deny the ads.”

On social media Tuesday, BART repeatedly responded to riders outraged by the ad’s appearance and presence.

Oh look, BART leadership making bad decisions again. https://t.co/rWqahQcDPz — AntiDisplacementCoup (@AsterZephyrIsis) September 12, 2018

We don’t endorse these ads. Free speech court rulings against transit agencies that have denied ads have made it clear that we must post these ads and allow advertisers to express a point of view without regard to the viewpoint. — SFBART (@SFBART) September 12, 2018

Are you actively seeking legal advice to find ways to legally take these down or prohibit them? I would like to see that you've made a sincere effort and exhausted the options. Otherwise it's just resignation. — Prettiest Pancake In The Stack (@dsa_hasan) September 12, 2018

Yes we sought legal advice in an effort to reject them. We even made the group remove their website url based on the content of the website. They did but what was left "History Matters Institute for Historical Review" couldn't be rejected and are protected by free speech rulings. — SFBART (@SFBART) September 12, 2018

Staff writer Rick Hurd contributed to this report. Contact George Kelly at 408-859-5180.