The purpose of an argument is to show why something is true. Saying an 'expert' believes something is true does not show why it is true nor that it is true. Deferring to Wiles is just ceasing to argue.
I see it as being more along the lines of there have been entire books written on the subject by people with more expertise than me that can cover the matter in far greater detail than a mere email. If the questioner is truly curious, then he has a resource to indulge his curiousity. If the questioner is acting in bad faith, then all of the information in the world isn't going to change his mind.
I know I should be "deferring to Wiles" here too, since you are oblivious to what's being said in response. There are certain things that we take for granted: like gravity. Or a round Earth. If some flat-earther comes over and starts asking you to prove that the Earth is flat, or that gravity is not just little gremlins pulling on your jeans, then I think it's safe to "defer to an expert".