Ba wrote on social media in 2020 that Mario Machado, founder of several extreme-right movements in Portugal, was "one of the main figures in the murder of Alcindo Monteiro", a Black man who was beaten to death in 1995 by skinheads in a wider, violent racist attack.
Eleven people were convicted in 1997 over the murder of Monteiro, but they did not include Machado.
Machado, who filed the defamation suit against Ba, has served time behind bars for racial discrimination and other crimes and uses social media to spread racial hate.
Machado, 46, was part of the group of skinheads who took to Lisbon's streets on June 10, 1995, to attack Black people and was found guilty of inflicting "bodily harm" on other Black people, but not Monteiro, on the same night.
Monteiro, 27, died from his injuries. The court ruling convicting the 11 of Monteiro's murder also said each individual who took part in the attacks on that night was responsible for the "event's entirety".
Still, Portugal's prosecutor's office agreed a year ago to pursue the defamation complaint against Ba filed by Machado, who has been in and out of prison for various crimes such as possession of illegal weapons.
The case has turned the spotlight on structural racism in Portugal, with the association where Ba works, SOS Racismo, saying the justice system was trying to "silence voices who fight for democracy".
Judge Joana Ferrer said on Friday Ba's post stated "a false fact that indisputably damaged his (Machado's) honour" as "he did not murder Alcindo Monteiro".
Machado's lawyer Jose Castro hailed the ruling as showing "a rule of law free from political pressure".
Ba's lawyer Isabel Duarte said she would appeal the court decision and take it to the European Court of Human Rights if needed, adding: "The state allowed the extreme-right to penetrate its institutions."
($1 = 0.9448 euros)
(Reporting by Catarina Demony; Editing by Susan Fenton)
By Catarina Demony
