The right to quote allows the use of copyrighted text with limits that are followed by OpenAI

https://en.wikipedia.org/wiki/Right_to_quote

I think your copyright argument is focused on media, like music. This appears be a specific exception that applies to text. Music sampling for example is a direct copy of the recording but quoting text, even though it's a copy, is a new work because although the words are the same it's not the original copied (as in the quote is written or typed by OpenAI).