It’s not clear how successful radical extremists have been so far in this regard, because there are no reliable figures that take full account of Christian emigration from Egypt. But certainly, anecdotally, it would appear that Christians have left in far greater numbers over the last few years and that internal migration of Christians has also increased. Some within this group—one that has been protected in Egypt since the dawn of Christianity—now wonder whether this moment represents the dusk of their community in Egypt.

It would be comforting to think that this is purely about ISIS. And it’s true that ISIS is the main militant threat against Christians, and against wide swathes of other Egyptians more generally. ISIS doesn’t simply target Christians; ISIS targets Egyptians in Egypt, as it targets Iraqis in Iraq, and others in other countries.

But ISIS also feeds off a preexisting sectarianism that provides a certain type of background music for ISIS activities. Huge swathes of the Islamist camp in Egypt cannot claim to be putting forward a vision of genuine respect in the country, even though they may condemn Friday’s attack. In much of the pro-Islamist media, the Arabic-language discourse around Christians is clear, and clearly more negative than the discourse that appears in English-language media used for PR purposes with the West.

Sectarian incitement and anti-Christian populism are not limited to the ISIS cohorts and cells in Egypt. ISIS may take the sectarianism to an ultimate conclusion, but before ISIS ever existed in Egypt, a vile sectarianism had already infected far too much of the pro-Islamist universe. It has spread by playing to the baser, more populist sentiments among the pro-Islamist camp.

As Taylor Luck noted earlier this month in the Christian Science Monitor, Muslim antipathy toward Christians has been simmering for a long time, and has occasionally erupted into mob violence:

One of the largest waves of anti-Christian violence was after the 2013 military ouster of Islamist President Mohammad Morsi … and the army’s bloody crackdown against a sit-in by Muslim Brotherhood supporters in which nearly 1,000 Islamists were killed. Brotherhood officials singled out Copts, and particularly Coptic Pope Tawadros, for being complicit in the General Sisi-led military coup, and Christians were the target of angry supporters. In August 2013, Human Rights Watch reported that mob violence led by Brotherhood supporters damaged 42 churches and dozens of schools and businesses owned by Copts across Egypt, killing several and trapping Christians in their homes. Islamist circles and some Muslims across Egypt, meanwhile, use rhetoric deriding Christians as a “favored class” that is “hoarding wealth” and benefits from the regime, fault-lines that ISIS is looking to exploit.

We shouldn’t group all of the Islamist camp, whether in Egypt or otherwise, together with ISIS; that would be inaccurate. But at the same time, we have to acknowledge that ISIS thrives on sectarian background music that has long been provided by other parts of the Islamist universe, and not only by ISIS’s own media apparatus.