For me it is pretty clear. My father, mother and step-mother went to Oxford. And so did all their fathers and three out of four brothers ( C Booker went to the other place). I was born in Oxford and somehow managed to scrape a place there too as did my youngest sister Naomi. And so naturally I support Oxford. Evil Knievil was born in Oxford and his father taught at Oxford and Evil was (understandably) rejected by Cambridge. And so he too supports Oxford.
My sister Tabby went to Cambridge and so as well as supporting ideas such as global warming and welfare hand-outs all round she also supports the ‘tabs. There is a consistency in her thinking.
But most people who do not regard this institution as elitist nonsense seem to support one side or other and for the oddest of reasons. I cannot say that I have any great feelings of warmth for the City of my birth, the City of Lost causes. I do not really care who wins most Varsity contests. But the Boat race is a bit different. Come on the dark blues. Or is it the Light blues. I can never remember which is which. Come on Oxford.