This phenomena is called 'Reputation'. It's not a replacement for evaluating the value of opinions, but it is a short cut.

If Breitbart et al have earned a reputation of being white nationalists, and others use that reputation to evaluate whether they want to consume their media, that seems totally reasonable. If Breitbart wants to eliminate that reputation, they can by regularly pushing content that discredits it.

Consider Buzzfeed, who is slowly turning their reputation around. It takes work, and more than one article with good individual content. You have to show a commitment to change, regularly, before that reputation changes.