I wonder various things about the display in the cathedral, and haven't come to any firm conclusions about it...
Banksy could be coined as a graffitti artist (and was when he started out) - he's defacing public property, after all, but because 'people' have decided that for whatever reason his work has now crossed the boundary into 'art' (the points he makes or the reactions he gets, or the fact he's anonymous?) his work now sells for silly amounts of money.
It begs questions about what is art, who decides what 'art' is (or isn't) and therefore what its value is, in monetary and other terms. If van Gogh had painted his sunflowers painting for the front of a seed packet, would we hold it in such high regard? And so because this is graffitti, and in a cathedral, have we decided it's not 'art' and therefore not of any value?
Any decent art will get a reaction. To have people look at your work and go 'Meh' is probably the worst thing for an artist. Love it or hate it, both are reactions, and this has certainly got people talking - about the nature of religious buildings, what is or isn't appropriate in them, and so on.
I wonder if many of the people who are reacting to the display ever darken the doors of a church from one year end to the next, or put money in the collection to keep the buildings maintained. I wonder if the display somehow offends their view of what a church or cathedral 'should' be, but churches are far more than just old, quiet, open buildings for people to wander into when they want. They are often busy places - cathedrals particularly - where humanity in all it's good and grimy glory wanders in, especially in the city centres. They're places where faith and humanity jarr at times, and so in some ways, this display mirrors some of that, and asks questions that we should probably all be asking.
Churches have always had art in them - stained glass windows and medieval murals for starters, and it was the Reformation that got rid of a lot of this from our churches. So in some ways this isn't new, and I'm sure loads of us have been in old churches and seen names carved into pews or stone by past church goers in a bored moment..... there is nothing new under the sun.