He didn’t read the book
We’re going to be completely honest here. We didn’t read The Great Gatsby back in high school. Heck, we haven’t read the book at all! But after searching on Wikipedia, it’s about a novel starring Leonardo DiCaprio, right? If you’re more learned than us, please inform us what Leo does in this book.
But if we’ve never claimed that everyone who went to high school has read this book. This genius really should look at himself before trying to take someone down a peg. If this line really is from the book, this commenter sure showed this random, non-Gatsby-reading fool.