Republican campaign strategist Steve Schmidt praised the teenager.
“Maybe that’s what happens after you’ve been down range of an AR-15 that kills your classmates and comes close to killing you,” Mr Schmidt told MSNBC, referring to the type of semi-automatic rifle used in the 14 February attack that claimed 17 lives.
“You lose all fear. Because this kid’s not scared. He’s not scared of the NRA. He’s not intimidated and scared by Laura Ingraham.”
On Wednesday, Ms Ingraham posted on Twitter: “David Hogg Rejected By Four Colleges To Which He Applied and whines about it.”
David had mentioned to celebrity gossip website TMZ a day earlier that he had been turned away from four colleges in the University of California system.
On Thursday, the Fox presenter struck a conciliatory tone, praising David’s grades.
“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,” she said.
But a TripAdvisor spokesperson said Ms Ingraham’s original comments “cross the line of decency”.
Wayfair said “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”.