Breitbart is encouraging a boycott of Kellogg's products after the cereal maker said it would no longer advertise on the news and opinion website, formerly run by President-elect Donald Trump aide Steve Bannon.
The Kellogg Company cited company "values" in explaining its decision; a spokeswoman said Thursday it has "nothing to do with politics."
Breitbart has been condemned for featuring racist, sexist and anti-Semitic content.
Breitbart said Kellogg's decision amounted to "economic censorship of mainstream conservative political discourse" and "as un-American as it gets." It launched a #DumpKelloggs petition Wednesday calling for a boycott of Kellogg's. More than 134,000 had signed the petition as of Thursday afternoon, according to the site.
Breitbart said Kellogg's decision represents "an escalation in the war by leftist companies like Target and Allstate against conservative customers" and their values.
Target and Allstate also have reportedly pulled ads from the site.