A Syrian schoolboy who was the victim of a video smear by far-right activist Tommy Robinson was devastated by the character assassination, a UK court heard.
Jamal Hijazi, 17, faced death threats and "extremist agitation" after a video of him being attacked by bullies was posted online, London's High Court was told.
Mr Robinson, a founder of the English Defence League, "turned Jamal into the aggressor and the bully into a righteous white knight", Mr Hijazi's lawyer said.
Mr Robinson, 38, whose real name is Stephen Yaxley-Lennon, is being sued in a libel trial by Mr Hijazi, whose family are refugees from Homs.
Mr Hijazi was a pupil at Almondbury School in Huddersfield, northern England, when he was attacked in the playground.
Mr Robinson posted videos of the incident and made the allegations against Mr Hijazi in two Facebook videos that
were watched by nearly one million people.
Catrin Evans QC, representing Mr Hijazi, said the allegations – which Mr Robinson denies – had "a devastating effect on Jamal and his family" and led to them being relocated.
She said Mr Robinson "falsely accused Jamal of being part of a gang that participated in a violent assault on a young girl and … also alleged that he had threatened to stab another child" and did so "without any direct knowledge of the events in question".
Ms Evans told the court her client was subjected to bullying shortly after he started at the school in October 2016.
“The bullying, and the failure to do enough about it, culminated in 2018 in a series of incidents in the school, including serious threats made to Jamal,” she said.
Ms Evans said a fellow pupil attacked him in October 2018 and “simulated waterboarding him” by pouring a bottle of water over his face when he was on the ground.
She called Mr Robinson "a well-known, extreme-right advocate with convictions for violence", who "used his social media platforms … to spread his extremist views".
She described his defence as "a cobbled-together mix of generalised smears of Jamal's character" and said there was "simply no merit to the defendant's defence of truth".
Mr Robinson, who is representing himself, defended his comments on the basis they were substantially true.
In written submissions, he said he had "uncovered dozens of accounts of aggressive, abusive and deceitful behaviour by the claimant, including acts which speak the truth to the matters complained of".
Mr Hijazi and Mr Robinson are expected to give evidence in an eight-day trial at the Royal Courts of Justice in London.