The poisonous atmosphere that my supporters and I created at Newham College grew so dangerous that in 1995 my self-appointed bodyguard stabbed to death a non-Muslim student on campus, to cries of “Allahu akbar!” The killer, Saeed Nur, was convicted of murder.

I was rightly expelled from the college, though my activism did not end there. I worked first in Pakistan and then in Egypt to recruit young military officers to Hizb-ut-Tahrir’s revolutionary agenda. In 2001, I was arrested by President Hosni Mubarak’s secret police. During four years in a Cairo prison, I gradually reconsidered the ideology of Islamism, and eventually abandoned it. On my release, I took up the human rights and counter-extremism work that occupies me now.

The Islamic Society at the University of Westminster, like others at universities across Britain, is still targeted by entryist radicals. While such institutions must guard free speech, they should also be vigilant to ensure that speakers are not given unchallenged platforms to promote their toxic message to a vulnerable audience.

These speakers claim to preach Islam, but they peddle a highly politicized, often violent strain of my faith. It is easier than one might think for bright, capable people like Mr. Emwazi to fall for the myopic worldview of the preachers of hate. Young people from relatively prosperous, educated backgrounds have long been overrepresented in jihadist causes.

Just last month, Britain was thrown into consternation to learn that three young women, teenagers from the Bethnal Green Academy, had slipped out of the country to join the Islamic State. Kadiza Sultana, Amira Abase and Shamima Begum were all, according to their parents and peers, straight-A students.

Challenging the notion of statehood, democratic theory and Middle Eastern power politics certainly takes a degree of intellectual sophistication, but it does not make an idealistic young person less vulnerable to exploitation by skilled recruiters. Regardless of good grades, they may suffer from a crisis of identity or grievances that radicalizers can prey on.

The desire to impose any religion on society is an inherently repugnant idea, but it is not so among many British Muslims. For decades, we’ve allowed Islamist ideologues to work unfettered across our communities, to the extent that Islamism has become the default form of political expression for many young Muslims in Britain and across Europe.

The leap from being an ordinary British teenager to joining the Islamic State is huge. But it is a much smaller step for someone raised in a climate in which dreams of resurrecting a caliphate and enforcing a distorted form of Islam are normalized. Until we confront this seeming legitimacy of Islamist discourse at the grass roots, we will not stop the scourge of radicalization.