AppNexus has taken a stand against Breitbart News, by barring it from using its ad-serving technology, for violating the digital advertising service’s ‘hate speech’ rules.

AppNexus performed a ‘human audit’ and found the controversial right-wing news site to be in breach of the rules, on several occasions in both articles and headlines.

Speaking to Bloomberg, AppNexus spokesman Joshua Zeitz stressed that the publication is not being targeted for its editorial positon or its spreading of fake news – making it clear the blacklisting was solely caused by the hate speech violation.

Although Breitbart does not buy ads directly from AppNexus, it purchases ads through automated online networks and exchanges. Breitbart will no longer get ads from AppNexus’ exchange.

AppNexus’ decision highlights the problem many technology companies face in their policing of online hate without limiting free speech. The move may put pressure on other major ad sellers, such as Google and Facebook, to take a similar stance, as both struggle with the rise of fake news.

The news will come as big blow to US President-elect Donald Trump after his recent anouncement that he would be hiring Breitbart News chief Stephen Bannon as chief strategist. Breitbart was heavily scrutinised for its stance during the recent US Presidential election.