Imam Shakeel Begg of Lewisham Islamic Centre sued after being accused by Andrew Neil on the Sunday Politics show of espousing “extreme beliefs”.
The judge said Imam Begg had “hidden his true views” behind a cloak of respectability.
Mr Justice Haddon-Cave said: “…he clearly promotes and encourages violence in support of Islam and espouses a series of extremist Islamic positions.
“On occasions when it has suited him…he has shed the cloak of respectability and revealed the horns of extremism.”
Imam Begg is very influential among British Muslims, especially the youth.
He has been involved in inter-faith initiatives with Jewish and Christian community leaders.
Imam Begg had previously appealed to ISIS to spare the British hostage Alan Henning.
A spokesman for the BBC welcomed the ruling against Imam Begg who now faces a significant legal bill.
Speaking to 5Pillars, Imam Begg said: “I am very surprised by the judge’s ruling. The judgement is clearly at odds with my own views and with the positive case that was presented and in particular, the interfaith and community work that I am engaged in.
“I am considering all options, including appealing the decision and the basis of the case not being adjudicating impartially, as well as the manner in which the judgement has been presented that indicates a closed mind towards my case.”
Sources close to Imam Begg told 5Pillars that the judge had merely regurgitated what the BBC’s academic “expert” Dr Matthew Wilkinson said, who has been frequently used by the Crown Prosecution Service (CPS) in anti-terrorism cases.
You can read the full judgement here.