Ignoring how it even applies to pure links with no content ("click here"), a lot of the previews you see on Facebook are using special meta tags that're added to news articles for that purpose. If the news orgs think that using that content for a nice preview of their article is bad for them, they should stop deliberately providing it.

(I think the `og` meta tags are a better argument here than `robots.txt`, because the former is the news orgs actively helping their content get redisplayed, while the latter is Google they-would-argue saying "we're stealing this unless you tell us not to", which sounds far sketchier.)