> those who consistently take anti-establishment stances, often without merit, barely get a footnote

"anti-establishment" as in holding the government accountable and asking questions of them -- irrespective of which party is in power?

isn't that the job of news media?

if they are doing it consistently - good on them.

why does it need a footnote or disclaimer?

I am sure there is enough content to file under a "Controversies and Crticism" section on the page of every anti-establishment media house. Volunteers are free to add.