I don't agree with his interpretation. As I understand it, the long tail as applied to business just means that there is a significant chunk of the market made

I don't agree with his interpretation. As I understand it, the long tail as applied to business just means that there is a significant chunk of the market made up of a big number of small items. You wouldn't try to disprove this by showing that blockbuster movie releases make up a huge portion of the movie industry, or that Spotify is a big player in the music industry, or that Amazon is a big player in the retail space, because the long tail doesn't preclude those things. If you wanted to argue against the existence of a long tail, you'd say something like "if Netflix got rid of everything except a few, very successful movies, their subscription revenue wouldn't change much", or "most people who pay for Spotify would keep paying even if the least popular 95% of the artists left" or "people don't value the fact that they can buy pretty much anything they can think of on Amazon," all of which seem like obviously incorrect statements (with no data on my part to back that up). The existence of aggregators doesn't disprove the long tail, you just have to talk about the long tail in terms of what people do inside those aggregators.