First of all, we are all unworthy.
Since Churchmen and Canon lawyers cannot seem to agree on this, I think that we should leave these decisions to the actual Pastor/Bishop in charge of the persons soul.
If the priest in question felt so strongly, he should have discussed his reservations with Mr. Biden ahead of time. My understanding is, that is they way it should be done. My understanding is also that the priest in question did not do any of this, just waited for Mr. Biden to get in line and refuse him in front of everyone.
A pastor of souls should not humiliate anyone like that.