facebook is "dark web"[0], everything in my gmail folders is "dark web", anything that john q. public can't see on the internet is literally "dark web"/"dark net" - that is, greater than 90% of all content behind a URI/URL is "dark" - unsearchable.

That the media and politicians use it as a negative connotation speaks volumes. "Dark whatever" != illegal content.

[0] facebook by virtue of their php lineage and gatekeeping have made (and kept) most of the content behind their own walls; unsearchable on any search engine - ironically, this includes their own. contrast this to something like reddit or stackexchange, which will gladly show up in search results.