One argument is that people who read a lot of books know quality. But I don't buy it: maybe people who read a lot of books have different tastes. And in any case, that just reinforces my definition: quality is what a certain (elite) group of people say it is.

Another argument is that complex books are better than simple ones. But that just means elite taste-makers like complex books, maybe because they've read so many books that straightforward ones are boring to them. But there's value in books that are easily understood--that's the whole point of writing: to communicate. One shouldn't value opaque books just because they're opaque.

Yet another argument is that smart people like good books and dumb people like popular books. Smart people are able to appreciate good books that are beyond most people. The convenient thing about this is that you can show how smart you are by liking certain books, which is way easier than winning a Fields Medal or Nobel Prize. Snark aside, this is just defining "good books" as "books smart people like", which is (in my view) morally equivalent to "books high-status people like".

As for "discouraging people from talking about things," I'm not yet arrogant enough to think that my post on Hacker News(!) is going to influence anyone. But if I did, I would tell people to stop worrying what other people think. Stop worrying about whether others think you're a snob or a mid. Like what you like and talk about it as much as you want.