Dear Magdalen College,
I, like many other candidates who have not been accepted to your university, am writing pre-emptively to reject any offers you may put my way. I sincerely hope you understand that you were in competition with many other universities who have not accepted me, and I simply cannot accept all possible offers that are not yet put to me.
I hope you find many other not-accepted candidates who are willing to attend your university in my stead.
On a side note, I read the (actual) letter, and the final sentence is "Perhaps you should offer a glass of water in your interviews; it is rude to torture your guests". The use of torture there is bold, to say the least. One could suggest that real torture victims in Guantanamo might say they get arguably too much water during interviews. It's a fine line between "Satiating Thirst" and "Waterboarding", and frankly, if a college doesn't want to accidentally stray across that line, I can respect that.