Behind closed doors, Internet companies routinely make tough decisions on content.

Apple and Google earlier this year yanked a mobile application produced by Hezbollah. In 2010, YouTube removed links to speeches by an American-born cleric, Anwar al-Awlaki, in which he advocated terrorist violence; at the time, the company said it proscribed posts that could incite “violent acts.”

ON rare occasions, Google has taken steps to educate users about offensive content. For instance, the top results that come up when you search for the word “Jew” include a link to a virulently anti-Jewish site, followed by a promoted link from Google, boxed in pink. It links to a page that lays out Google’s rationale: the company says it does not censor search results, despite complaints.

Susan Benesch, who studies hate speech that incites violence, said it would be wise to have many more explanations like this, not least to promote debate. “They certainly don’t have to,” said Ms. Benesch, director of the Dangerous Speech Project at the World Policy Institute. “But we can encourage them to because of the enormous power they have.”