Few left-wing pressure groups are as vicious and mendacious as the Southern Poverty Law Center. Founded in 1971, the SPLC today mainly exists to smear opponents of full-spectrum progressivism as “bigots” and “extremists.” Once the Montgomery, Alabama-based outfit mislabels an individual or an institution this way, it becomes nearly impossible to clear the taint, since many reporters mistake the SPLC for a bona fide rights watchdog.

So it’s good to see the SPLC held to account for at least one of these smears. On Monday, the group publicly apologized to Maajid Nawaz and agreed to pay his organization, the Quilliam Foundation, some $3.4 million to settle a defamation suit.

The SPLC in 2016 included Nawaz, who has spent years peacefully combatting both Islamism and anti-Muslim bigotry in Britain, in its Field Guide to Anti-Muslim Extremists, alongside a litany of genuine haters. As evidence, the SPLC cited the fact that Mr. Nawaz had once tweeted a cartoon of the Prophet Muhammad “despite the fact that many Muslims see it as blasphemous.” Dissidents across the Muslim world and in too many Muslim communities in the West risk beatings, torture, and worse for daring to criticize their religion and its founder. The SPLC in effect lent its liberal, “civil-rights” imprimatur to their mistreatment at the hands of their coreligionists.

“Given our understanding of the views of Mr. Nawaz and Quilliam,” SPLC President Richard Cohen said in a statement, “it was our opinion at the time that the Field Guide was published that their inclusion was warranted. But after getting a deeper understanding of their views and after hearing from others for whom we have great respect, we realize that we were simply wrong to have included Mr. Nawaz and Quilliam in the Field Guide in the first place.”

Damn right. But Nawaz wasn’t the only victim of SPLC smears. Another was the Somali-born author and activist Ayaan Hirsi Ali, who has written for these pages. In the same Field Guide, the SPLC seemed to question Hirsi Ali’s personal story–she suffered genital mutilation in her native land–and accused her of bigotry for emphasizing the religious and ideological dimensions of Islamic terrorism. She, too, deserves a retraction and apology from the SPLC.

As for journalists who regularly rely on SPLC, the religious-liberty law firm Alliance Defending Freedom, another victim of the group’s smears, got it exactly right in its statement on the Nawaz settlement: “SPLC has become a far-left organization that brands its political opponents as ‘haters’ and ‘extremists’ and has lost all credibility as a civil-rights watchdog . . . SPLC’s sloppy mistakes have ruinous, real-world consequences for which they should not be excused.”