“In 1982, as chairman of the Hornsey constituency party, Jeremy Corbyn signed a membership card for Tariq Ali, a former member of the International Marxist Group, in defiance of Labour’s National Executive Committee. He also campaigned against the expulsion of the Trotskyist Militant Tendency from the party, acting as the “provisional convenor” of the “Defeat the Witch Hunt” campaign. “If expulsions are in order for Militant, they should apply to us, too,” he argued.”
https://www.newstatesman.com/politics/uk/2018/03/meaning-corbynism