(Corrects first paragraph to say last week's rampage, not this week's)
By Barbara Goldberg and Gina Cherelus
NEW YORK, Feb 23 (Reuters) - The fallout over last week's shooting rampage at a Florida high school started to take its toll on the National Rifle Association's roster of corporate partners on Friday as a half dozen companies severed marketing ties with the gun advocacy organzation.
The exodus of corporate names, ranging from a major insurer to car rental brands and a household moving company, occurred after the NRA launched a counter-offensive against a student-led campaign for tighter U.S. gun ownership laws.
At the same time, gun control activists are stepping up pressure on Amazon.com Inc and other online streaming platforms to drop the online video channel NRATV, featuring gun-friendly programming produced by the NRA.
Moms Demand Action for Gun Sense in America, founded after 20 first-graders were shot and killed at a Connecticut school in 2012, sent letters to Apple Inc, AT&T Inc, Amazon, Alphabet Inc's Google and Roku Inc on Friday, asking them to drop NRATV from their platforms.
"We have been just disgusted by NRATV since its beginning," Shannon Watts, founder of the Moms Demand Action group, told Reuters. "It tries to pit Americans against one another, all in an attempt to further their agenda of selling guns."
AT&T said it does not carry NRATV. None of the other companies immediately responded to requests for comment.
The issue of gun control, and the NRA's role in opposing it, became the focus of renewed national debate on Feb. 14, when a former student killed 17 people at Marjory Stoneman Douglas High School in Parkland, Florida, with an AR-15 assault rifle he had purchased legally.
The U.S. Constitution's Second Amendment protects the right of Americans to bear arms. The NRA, which has long used campaign donations and effective lobbying to command political influence, argues that stricter gun control would erode individual rights. The group has not commented on companies cutting ties.
Angry student survivors of the shooting have confronted politicians from state lawmakers to U.S. President Donald Trump himself, demanding stricter gun control laws.
In response, the NRA and Trump have suggested arming teachers who have received training to deter attackers, a proposal that has been met with skepticism by teachers unions and gun violence experts.
Before the corporate defections, nearly two dozen companies nationwide had offered incentives to NRA members, according to ThinkProgress.com, a news site owned by the Center for American Progress Action Fund.
The attrition started late Thursday when three rental car brands owned by Enterprise Holdings Inc said they were ending discount programs, and First National Bank of Omaha said it would not renew the NRA's contract to issue a co-branded Visa card.
By Friday, the list of defectors expanded to include Symantec Corp, which ended an discount program for its LifeLock identity theft product. Home security company SimpliSafe and Hertz Corp also terminated discount programs.
Chubb Ltd said it would stop underwriting a NRA-branded insurance policy for gun owners that covers legal costs in self-defense shootings. Another insurer, MetLife Inc , also said it had ended an auto and home incentive program for NRA members. And North American Van Lines said it was scrapping its an affiliate relationship with the NRA.
David Hogg, one of the student survivors of last week's attack who launched the #NeverAgain anti-gun violence movement, said the students would target any company with ties to the NRA, in addition to lawmakers who accept donations.
About a dozen other companies with marketing ties to the NRA, including FedEx Corp and Hertz, which offer discount programs, did not respond to requests for comment.
Activists have also called on public pension funds to divest from gun maker stocks, which were broadly lower on Friday.
Meanwhile, an online campaign using the Twitter hashtag #StopNRAmazon picked up steam, putting pressure on Amazon CEO Jeff Bezos to drop the channel. Many of those tweeting are in the entertainment industry.
"Ironic how the @NRA likes to point a finger at what kids watch on TV ... while they spew vile rhetoric on NRAtv, streamed on @Amazon and aimed solely at boosting gun sales," wrote screenwriter Randi Mayem Singer.
Moms Demand Action, which sent the letters to the streaming platform, also posted an online petition using the hashtag #DumpNRATV.
"To be affiliated with them, whether you are a company or a lawmaker, it is not going to pay off in the long run," said Watts, the group's founder, signaling the start of a broader campaign. "Doing business with the NRA is clearly bad business."
The target of its ire is NRATV, which describes itself as "America's Most Patriotic Team on a Mission to Take Back The Truth." The channel features programming that leans heavily on speeches by NRA chief executive Wayne LaPierre and spokeswoman Dana Loesch.
Yet another campaign, using the hashtag #BoycottNRA, was the top trending topic on Twitter on Friday morning.
The push is the latest effort by social activists to use social media to apply economic pressure to force change.
Last April, Fox News parted ways with television host Bill O'Reilly when sponsors started to drop his show in the wake of sexual harassment allegations against him.
Similarly the National Football League announced a tougher policy on handling domestic violence accusations against players when its marketing partners applied pressure for changes.
Reporting by Barbara Goldberg and Gina Cherelus in New York; Additional reporting by Suzanne Barlyn in New York, Andrew Hay in Taos, New Mexico, and Arunima Banerjee in Bengaluru; Writing by Joseph Ax; Editing by Frank McGurty and Grant McCool