Bannon worked as executive chairman of Breitbart News until he left to run Trump's campaign. He was scheduled to return to Breitbart, but earlier this month, Trump named Bannon his chief strategist, stirring more of the site's critics to call out its content and appeal to its advertisers.
"We regularly work with our media buying partners to ensure our ads do not appear on sites that aren't aligned with our values as a company," Kellogg spokesperson Kris Charles in a statement.
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"This involves reviewing websites where ads could potentially be placed using filtering technology to assess site content. As you can imagine, there is a very large volume of websites, so occasionally something is inadvertently missed. In this case, we learned from consumers that ads were placed on Breitbart.com and decided to discontinue advertising there."
Breitbart News couldn't be reached for comment. But in an interview with The Hollywood Reporter, Bannon has claimed that he was not a White nationalist, as many liberals assert. "I'm not a white nationalist, I'm a nationalist. I'm an economic nationalist," Bannon said.
Other companies have already said on Twitter that they will stop advertising on Breitbart. They include pharmaceutical manufacturer Novo Nordisk, eyeglasses maker Warby Parker and the San Diego Zoo.
AppNexus, one of the largest online advertising networks, also blocked Breitbart News.
Contributing: The Associated Press