Veterans groups who stood up to Donald Trump’s pandering to their ranks are now routinely bombarded with nasty messages from the mogul’s supporters, who want to punish them for daring to challenge their leader.

Paul Rieckhoff, the CEO of Iraq and Afghanistan Veterans of America, learned this firsthand when he stood up to the Republican presidential frontrunner in late January, saying he would decline any donations from Trump’s charitable foundation if offered.

“We’ve gotten a flood of nasty attacks… many scary and threatening emails, [the] worst social media trolling I’ve ever seen,” Rieckhoff told The Daily Beast. “Showing what happens when you simply say no. This is the climate he’s created with his followers.”

Rieckhoff had plenty of reasons to pre-emptively reject the donation. Trump has repeatedly insulted veterans, but on the campaign trail has tried to use them for political gain. After a squabble with Fox News over the use of Megyn Kelly as a debate moderator, Trump held a competing event, ostensibly to raise money for veterans groups.

The businessman’s record hasn’t hobbled his candidacy, and he leads in South Carolina despite the massive veterans community there.

So when Rieckhoff said he didn’t want his organization to be used as a political prop, and pre-emptively declined any proceeds from Trump’s fundraiser, the businessman’s fans directed wave after wave of viciousness against IAVA and its CEO on Twitter and Facebook.

Rieckhoff was called a “fucking scumbag” by one commenter, then told by another to “get off your ass and get the funding or get fired.” “Keep your mouth shut and take the money,” another Trump fan said. Added a tax-conscious individual: “I hope your asses get audited.”

Trump has a long history of controversial, even anti-veteran stances, despite his current claim that he’d be good for veterans if elected president. In the ’80s, Trump tried to throw disabled vet street vendors off Fifth Avenue, accusing them of essentially being a blight on the aesthetics of the street. Before his presidential campaign, Trump’s charitable foundation gave more to the Clintons than to veterans organizations. Plus, famously, Trump said Sen. John McCain’s time in a prisoner of war camp didn’t make him a hero: “I like people who weren’t captured.”

A number of groups in Iowa have benefitted from Trump’s fundraiser: Organizations like Puppy Jake, which provides service dogs to vets, and Support Siouxland Soldiers, both received six-figure checks. So did a small veterans charity in New Hampshire.

But when another veterans group went on the record against Trump, their phone lines and inboxes were slammed the next day with malicious fans.

“The next day, people called our office—that were very vile: People were issuing threats, they were calling our members ‘faggots.’ We had a very vitriolic response. They were saying things like, ‘We’re going to take down your group,’ even up to what could only be interpreted as physical threats: ‘You better watch out the next time you hold an event,’” said the executive director of a veterans advocacy group who wanted to stay anonymous, so as to spare his organization the “annoyance” of enduring it again.

“It was a distraction, and it was an annoyance that made staff incredibly uncomfortable,” said the executive director. “It was disturbing.”

Liberty House is a small, New Hampshire-based charity that focuses on housing formerly homeless vets and feeding the hungry. Its executive director, Keith Howard, was subjected to a similar experience after declining to appear with Trump at a political rally to accept a donation.

“So....you bunch of losers who can’t get on with your life except for bitchin’ about how mistreated you are don’t want Mr. Trump’s money. Well then shut the fuck up about what you don’t have and what you’ve done for your country. I hope all your funding dries up. You’d rather whine than be men,” wrote one angry individual by email, calling organization members “sissies.”

Howard sighed: “It’s a free country, and people have a right to write nasty emails,” he said. And he found that the angry messages were a symptom of Trumpmania that could be reasoned with.

“A fellow had emailed me about how bad I was to turn down the rally. I called and talked with him for about 15 minutes,” Howard told The Daily Beast. “The next day, he wrote me a very nice email thanking me for my time... Even the people who were negative were being knee-jerk negative instead of really having a reason for it.”