It’s the latest social media kerfuffle involving consumers, advertisers and content deemed offensive, at least by some and often along partisan lines, from outlets like Fox News and Breitbart News, as well as cultural institutions like Shakespeare in the Park. Calling for an advertiser boycott has become a common strategy since the presidential election. A group — in the case of Mr. Hannity, the liberal watchdog Media Matters — circulates a list of advertisers and urges people to contact them directly, particularly on social media.

This time, some companies have stumbled. Realtor.com said in a tweet over the weekend that “we are not currently, and will not be running TV ads on Hannity.” Later, it deleted the tweet and posted a statement on its website saying the company advertises across “dozens of television networks” and will continue placing ads on Fox News and its top shows.

“Some staff didn’t realize that we have a practice of not engaging in boycotts,” a spokeswoman said of the deleted tweet. “Senior management at Realtor.com became aware over the weekend of the error, and the tweets were taken down Sunday and the policy was posted on our corporate website.”

Volvo Car USA apparently responded to a tweet from a consumer on Monday to say, “We have spoken with our media agency and have advised them to cease advertising on the show.” But that message has disappeared. The company did not respond to requests for comment.