media bias

This "disease" is a somewhat tongue-in-cheek – though still quite real – phenomenon. Often, those who have been awarded a Nobel gain infamy for saying and believing incredibly stupid things, some of which are quite delusional. Mr. Krugman, the Nobel Prize-winning economist and columnist, is the newest inductee into this dubious club.
Facebook may be overtly partisan and secretly conspiratorial, but companies have the freedom to do that. The only thing that will absolve Facebook of blame is if government seeks to regulate them.