The terrible consequences of Islamic extremism are on display on a weekly basis around the world. In the days after Charlottesville, five men in Barcelona used a van and knives to kill 14 and injure scores of innocent people. Another Islamic extremist went on a stabbing rampage in Finland. In wealthy societies like the United States, most plots to kill in the name of Islamist supremacy are foiled. But poorer societies in the developing world lack the means to do that, which is why the majority of victims of the extremists are in countries like Afghanistan, Iraq, Nigeria, Pakistan and Syria.

It is not surprising that, when I point out such facts, I am viciously attacked and threatened by those who are dedicated to Islamic extremism. But it has always struck me as odd that so many supposed liberals in the West take their side rather than mine, as happened three years ago, when Brandeis University rescinded their offer to me of an honorary degree. I would have expected a civil-rights organization supposedly committed to justice to speak out against those who would oppress women, gays and people of other faiths. But the S.P.L.C. has nothing to say about Islamic extremists; only about their opponents.

Another voice the S.P.L.C. has tried to silence is that of Maajid Nawaz, who was included in the same field guide as me. (He is suing the organization for defamation.) Mr. Nawaz has written extensively about his past as an Islamic extremist in England and Egypt, just as I’ve written about my time in the Muslim Brotherhood as a teenager. For the past decade, he has run Quilliam, an organization dedicated to countering Islamic extremism in Britain and elsewhere, notably in Pakistan.

I met Mr. Nawaz in 2010 at a debate in New York City, where the subject was the nature of Islam. Our passionate disagreement was on full display: Mr. Nawaz is a secular Muslim, whereas I am not a believer any longer. Yet we both agreed the path to a successful reformation of Islam lies in more debate, more scrutiny and more critical thinking. It is exactly these activities that our opponents, now including the S.P.L.C., describe as extremism.

Cui bono? That question is nearly always the right one to ask of organizations like the S.P.L.C. Who really benefits from their activities? Repeatedly, and for more than a decade, journalists at publications ranging from Harper’s to Politico to The Nation to The Weekly Standard have pointed out that the center’s founders seem more interested in profiting off the anxieties and white guilt of Northern liberals than in upholding the civil rights of poor Southerners, or anyone else. There’s a less cynical explanation, though, which is that liberals are deeply and increasingly uncomfortable with calling out Islamic extremism for fear of being smeared as “Islamophobic,” or worse.

Regardless, the S.P.L.C.’s decision to target those who speak up for the civil rights of Muslims is a travesty.

Muslims today cannot freely debate the role of their religion in most Muslim-majority countries, where the charges of heresy or apostasy can mean a death sentence or a lynch mob. Here in the West, too, free discussion of Islam is getting harder not least because Islamic organizations like the Council on American-Islamic Relations pounce on any criticism of Islam, branding it “hate speech,” the modern word for heresy. Unwittingly or not, the S.P.L.C. is abetting Islamic extremists by branding critical thinkers like Mr. Nawaz and me “extremists.”

Taking a stand against the neo-Nazi display we saw in Charlottesville is an impulse that should be cheered — and Apple, JP Morgan and the Hollywood A-list can and should do more to counter political violence and intolerance in all its forms. But they need to find more trustworthy and deserving partners to work with than the S.P.L.C.