A number of advertisers have cut ties with a Fox News host after she publicly criticised a Florida school shooting victim and accused him of whining.
Since 17 students and teachers were killed in the Parkland attack, survivor David Hogg has become a leading voice in the March For Our Lives movement for stricter gun controls.
In response, the 17-year-old has been criticised by right-wing conservatives and gun advocates who have falsely called him a "crisis actor".
On Wednesday, Fox News host Laura Ingraham tweeted: "David Hogg Rejected By Four Colleges To Which He Applied and whines about it."
In reply, Mr Hogg tweeted a list of a dozen Fox News advertisers and encouraged followers to immediately call and ask them to drop support for Ms Ingraham's show.
Online home goods store Wayfair, travel website TripAdvisor and pet food firm Nutrish have since said they will be cutting ties with Ms Ingraham.
Wayfair said in a statement that it supports "open dialogue and debate on issues" but "the decision of an adult to personally criticise a high school student who has lost his classmates in an unspeakable tragedy is not consistent with our values."
TripAdvisor says it does not "condone the inappropriate comments made by this broadcaster" and said the statements aimed at the high school student "cross the line of decency."
Nutrish tweeted it was in the process of removing ads from Ms Ingraham's show.
The news host later apologised for her post, saying: "On reflection, in the spirit of Holy Week, I apologise for any upset or hurt my tweet caused him or any of the brave victims of Parkland."
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She added: "He's welcome to come on my show anytime for a productive discussion."
Mr Hogg said the apology was "not enough", adding: "I will only accept your apology only if you denounce the way your network has treated my friends and I in this fight. It's time to love thy neighbor, not mudsling at children."