Chomsky had stated earlier that there are experts to read who cover such things. The kid kept asking variations of the same question. If I were Chomsky I would have been done after a couple of responses.
"These 'experts' agree with me" is not an argument. Indeed, clearly Chomsky did not want to engage the argument so ceasing responding would have been logical.
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".
"These 'experts' agree with me" is not an argument.
What's your point in saying so? I would guess that Chomsky could care less about winning an Internet "argument" with some random dude. From his point of view, it's entirely reasonably to say "go read the literature and come back when you're more informed". If the other party doesn't want to do that, they have no moral claim to Chomsky's continued participation in the discussion.
Simply that it was odd that Chomsky continued the conversation when he didnt want to actually explain his point of view. His point that "why some people are poor" is well settled science answerable with a literature review is not being honest either.
You're only committing a "appeal to authority" fallacy if you contend that something is true because the person saying it is "an authority." Pointing out that someone is clueless on a topic and suggesting they read the literature and gain some baseline knowledge is not the same thing at all.
As to whether it is, as someone said above, "simply ceasing to argue" one can rightly say "so what?" None of us owe some random person on the Internet our participation in their argument. Time is valuable and it's entirely reasonable to check out of an argument or discussion and say "here, go read these books" if you don't stand to gain anything from continuing the dialog.