Just by way of a clarification. Joe McCann was a member of the Official IRA, not the Provisional IRA, and as such is unlikely to have had links with Sinn Féin. The OIRA enacted a ceasefire in 1972.
Even more than their more militarily active brethren in the Provo's, the OIRA where even more Marxist than the larger group.
Both groups along with their political wings are intent on turning Ireland into Cuba, just without the sunshine.
Joe McCann: Official IRA leader had sought a socialist Ireland
JAS