In what was no April Fool’s Day prank, three pairs of protesters at the University of Pennsylvania disrupted and ultimately shut down Friday’s talk by Central Intelligence Agency Director John Brennan. The lecture—hosted by two of my alma maters, the University of Pennsylvania Law School and Penn’s Fels Institute of Government Administration, and moderated by one of my former professors and mentors, former Congresswoman Marjorie Margolies—was intended to be a “conversation on modern foreign policy issues, national security, and the future of the global fight against terrorism.”

As reported in The Daily Pennsylvanian, a few minutes into the event, a pair of protesters stood up in the audience, held a sign and started chanting “drones kill kids” and “U.S. out of the middle east.”

Responding to the protesters, Penn Law Dean Ted Ruger and Professor Margolies both tried to spur a dialogue by asking the protesters if they wanted to hear Brennan’s response to their criticisms. But those pleas were ignored by the protesters. At one point, Dean Ruger asked the protesters “Are you trying to silence him?” After a roughly three-minute disruption, including chants of “black lives matter” and “murderers,” the protesters were escorted out of the event.

After the first protesters were removed, Brennan tried to address their criticism about the use of drone strikes. He held that “[President Obama’s] administration has made the criteria very rigorous as far as what are the conditions where such actions would be taken.” He continued:

“I know there are a lot of reports about hundreds upon thousands of innocents who have been killed as a result of these strikes…I can tell you with great confidence that those are exceptionally exaggerated reports… the number of civilians killed relative to the number of terrorists killed is a very small portion.”

Unfortunately, Brennan was soon drowned out by a second pair of protesters affiliated with Students for a Democratic Society, chanting, “U.S. out of the Middle East, no justice no peace.” Those protesters were also eventually escorted out of the auditorium.

Brennan was interrupted a third and final time during the question and answer portion of the event by yet another pair of protesters, chanting, “the CIA is a terrorist group; human torture is a crime.” The third protest lasted for over 15 minutes, and led the sponsors to cancel the remainder of the event.

Disruptions at events are all too common on college campuses, and, contrary to what disruptive protesters often argue, shouting down another speaker is not a valid exercise of the right to free speech. Events are typically open to the public or invited guests in order to address the topics chosen by the events’ organizers, with time often set aside specifically so attendees can question the speakers or challenge their arguments. While fleeting interruptions may in some instances be valid expressions of free speech, disruptions that prevent audiences from hearing speakers constitute heckler’s vetoes.

It is not for protesters to decide what voices may and may not be heard in someone else’s event. It is also not every day that critics and supporters alike have an opportunity to hear from and publicly question the director of the CIA. While FIRE takes no position on the merits of Brennan’s or the protesters’ arguments, we cannot help but note how unfortunate it is that the question and answer period was cut short. Instead of capitalizing on the opportunity to ask Brennan tough questions, the protesters prevented everyone from having a robust dialogue. It’s hard to see any benefit in that.