Social-media giant Twitter has been seeking to crack down on abusive and racist language. For instance, on Tuesday it hid a tweet by US President Donald Trump, labeling it “abusive behavior.” The tweet had said protesters might be met by “serious force.” This was considered abusive by Twitter.However, the website continues to host thousands of tweets that use the word kuffar, a derogatory Arabic term for non-Muslim unbelievers, as a form of abuse. Usually used by Islamists and far-right religious extremists against minorities and those they disagree with, it was often used by ISIS members in 2014 as a term of abuse directed at those they marked for genocide, such as Yazidis, Shi’ite Muslims and Christian minorities in Iraq.The term is nevertheless not labeled by the platform. For instance, a quick search reveals a tweet on June 22: “if you’re a feminist you basically believe that kuffar ideologies are better than the rights that Allah gave you.” That tweet is directed at feminists, who the user labels “unbelievers.”The way kuffar is used on Twitter often resembles the Nazi term Untermensch, or inferior and subhuman.Another tweet on June 24 attacked Iran as the “kuffar regime,” while another account with 9,000 followers the same day said that “kuffar must fear us and not vice versa.”On June 19, another user slammed Black Lives Matter and feminism, tweeting: “Muslims need to lead rather than be led by the kuffar,” insinuating that these movements are heathens. Viewers of a June 20 video were told by an extremist preacher to “strike terror in the hearts of the kuffar.”Hatred of US protesters, oddly, has also become part of the incitement campaign on social media. A user named Umm Suleiman said those “protesting with the kuffar,” referring to protesters in the US, are kneeling, which is “not permissible” in the religion. Zahed Muhammad wrote on June 21: “may allah allow these kuffar to die with kufr.”Users of Twitter have noticed that pro-ISIS members continue to use the site and call people kuffar, usually laced with other insults, such as calling women whores, who they object to. On June 21, a user named Ibn Ernest wrote about “being increasingly defined by the social media divides between the kuffar, as we become an extension of the kaffir civilization.” The term kaffir was a racist term of abuse for black people in South Africa. Yet both it and kuffar, used in an abusive war, are not flagged by Twitter. An extremist video posted on June 18, in which a religious scholar supposedly answers questions live, includes the explanation above it: “boxing is only allowed if you beat up kuffar.”A user named Akhand Bharat, in reply to a story about India, wrote on June 18: “u r a blot on the face of Islam, u r kuffar, shame on you for being a hard core left liberal.” Another man bashed a pro-LGBT post by writing: “filthy kuffar.” Another post said: “you kuffar are finally being kicked out of our lands.”There is no shortage of these tweets; the ones above are just the top examples of thousands or tens of thousands, maybe millions. Twitter has cracked down on extremist accounts and pro-ISIS accounts in the past. More than 1.2 million were removed by 2018, and swaths of pro-terrorist accounts have been done away with.Algorithms could flag the term kuffar and review tweets that use the term and call for terrorism, attacks, beatings, assaults on women and feminists or incite against LGBT and other people, including against minorities such as Shi’ites, or use the term as an abusive one. A review of the recent tweets suggests that it is almost always used as a term of abuse, not as an example or as a quote.