Late to this thread but I have to take some issue with this:
According to Wikipedia, McDonnell went to a local grammar school and then "began training to be a Catholic priest, receiving a Church grant to attend St Joseph's College, Ipswich,[11] a Roman Catholic boarding fee-paying independent school...before eventually deciding against the vocation at the age of 15 or 16".
I volunteer at a former Roman Catholic Seminary and boarding school which was set up some 200 years ago to offer a catholic education to boys of catholic families and to train young men for the priesthood. Naturally it was fee paying because all schools were then fee paying. When schooling became compulsory and free in the late 19th century there was no provision for this specifically catholic education. If parents wanted a specifically catholic education for their sons, fee paying schools were all that were available to them. If it was felt that the boy had a vocation and the parents were poor the local catholic diocese funded their education with a view to maintaining a supply of young men for the catholic priesthood.
These schools cum seminaries were the only route to the priesthood. There were a number of them up and down the country. The practice of diocesan funding was finally abandoned in the 70's when it was decided that it was too expensive and risky to fund boys from the age of 11 in the hope that they would become priests. This led to the demise of the 'school' element pf these institutions. We get frequent visits from old boys who left at after A levels at 18 to go to secular universities and to pursue a secular career. There is nothing unusual about it.
What I am saying is that these schools were a necessity for the catholic church. McDonnell's educational career at this institution was a perfectly normal, common experience for boys from catholic families, rich or poor. It wasn't a 'privileged' education as we now understand the term. So all this talk of 'hypocrisy' is nonsense. (do you not have a spell checker, Ug?)
I would venture to say that perhaps his christian upbringing made him alive to the injustices and inequalities in the world and, while he may not now be a practising christian (I have no idea if he is or not) Marxism is quite compatible with Christianity.