Influenced by family friends Peadar O'Donnell and Máirtín Ó Cadhain as well as his own parents growing up, Mac Aonghusa pursued Irish republican and socialist politics as an adult and was heavily involved in the Labour Party during the 1960s, at one point serving as its vice-chairman.

[2] As well as attracting awards, An Fear agus an Sceal also brought controversy; two interviews, one with Máirtín Ó Cadhain, one with Con Lehane, both criticised the measures practised by the Fianna Fáil government during World War II to suppress and imprison Irish republicans.

In 1958 Mac Aonghusa became, alongside David Thornley, Noel Browne, Owen Sheehy-Skeffington, and Desmond Ryan, a member of the "1913 Club", a group which sought to ideologically reconcile Irish nationalism and socialism.

Fianna Fáil would attempt to repeal proportional representation again in the late 60s, at which point Mac Aonghusa once again threw himself into the fight, leading a group called "Citizens for PR".

The branch came to advocate for expressly socialist policies (something previously avoided by the Labour party in conservative Ireland) combined with on-the-ground grass-roots campaigning.

Through the Sean Connolly Branch, both Mac Aonghusa and his wife began to develop significant influence over the leader of the Labour party Brendan Corish.

The introduction of the book proclaimed that Corish had developed a "brand of democratic republican socialism … broadened by experience and built firmly on Irish‐Ireland roots" and had rid the party of "do‐nothing backwoodsmen", thereby becoming the "first plausible and respected Labour leader in Ireland".

In 1966, alongside Máirtín Ó Cadhain and other Gaeilgeoirí, Mac Aonghusa counter-protested and disrupted the Language Freedom Movement, an organisation seeking the abolition of compulsory Irish in the education system.

Mirroring Mac Aonghusa's own position, the Youth League were Corish loyalists that open rebelled against the views of Labour's conservative deputy leader James Tully.

[2] In the aftermath of his expulsion from Labour, Mac Aonghusa expressed an interest in the social democratic wing of Fine Gael, which had been developing under Declan Costello since the mid-1960s.

[2][5] Upon the onset of the Troubles, Mac Aonghusa was initially supportive of Official Sinn Féin, however by 1972 he came to resent them and, through the Ned Stapleton Cumann, their secret influence over RTÉ.

During the Arms Crisis in 1970, Mac Aonghusa supported Charles Haughey and Neil Blaney, who stood accused of arranging to supply weapons to the Provisional IRA, in the pages of the New Statesman and other left‐wing journals.

In this time period, Mac Aonghusa warned editors not to reprint his material in the Republic of Ireland as there was a de facto ban on him, and indeed, official attempts were made to block the transmission of his telexed reports.

Mac Aonghusa's columns in the Sunday Press and Irish language paper Anois were accused of descending into self-parody in their stringent defences of Haughey.

Mac Aonghusa railed against his detractors at the Conradh na Gaeilge árdfheis that year, declaring that "The mind of the slave, of the slíomadóir, of the hireling and the vagabond is still fairly dominant in Ireland".

In the foreword to the book he wrote about James Connolly he released that year, Mac Aonghusa declared that "the abolition of capitalism is essential if the great mass of the people in all parts of the globe are to be emancipated"However, with the recent collapse of the Soviet Union in mind, Mac Aonghusa declared that the Stalinist regimes of Eastern Europe had not been socialist, and argued that the social democracies of Scandinavia (the Nordic model), were what James Connolly had envisioned as the desired socialist society.