I wonder how many people nowadays would even realise the significance of the detail of eating chicken on a Friday in the 60s. That came pretty close to apostasy. I'm not even sure that Mother Church would have forgiven it on grounds of force majeure in those days.
Another "good" Prod employer was Dockrell's, who were revered in Dublin folklore for giving their jobs back to the men who were interned during the War of Independence. On the other hand, Guinness's, at least up to the time of independence, contributed to the cause of empire by dismissing messenger boys when they reached military age, though I gather they would often employ them again as labourers after a period of service in the armed forces.
Drifting back to the barriers inside our heads, what kept Trinity College Protestant and Anglo-Irish right up to the 1970s was not so much its own policies as the attitude of the Catholic Archbishop of the time, John Charles McQuaid, who forbade Catholics to study there on pain of some sort of reserved sin - or was it even excommunication? That never stopped nationalists from regularly trotting out the fact that the place was set up by Elizabeth I to promote Protestantism in Ireland four centuries ago as vindication for their own bigotry.
The amount of mind control that we were subjected to by the extraordinary McQuaid-Dev axis would be absolutely incomprehensible to my children's generation.