John was radicalised in 1965 by the US war in Vietnam. He started taking an active part in protesting the war and for that was arrested in May in Canberra.
In 1966, John became editor of the Sydney University Labour Club's magazine where he argued for the need of an off-campus youth organisation to better promote the antiwar campaign. In October in Sydney, John was part of rebellious demos against US President Lyndon Johnson's visit.
Into 1967, John, his brother Jim and others tried to establish “Group X”, a radical youth group. It flopped. In May, they tried to form a broad youth group with the CPA. That didn't eventuate. In August, they found the Society for the Cultivation of Rebellion Everywhere (SCREW). In November, the SCREW changed name to Resistance.
Anti-Vietnam War protests became mainstream. Resistance changed name to Socialist Youth Alliance (SYA). Socialist Workers League (SWL) formed in 1972. Direct Action was published and John became its early editor. In 1974-75, John was based in New York reporting for US Trotskyist Intercontinental Press magazine, under pseudonym “Peter Green”.