Frances Fox Piven is not going into hiding. Not yet.

The 78-year-old leftwing academic is the latest hate figure for Fox News host Glenn Beck and his legion of fans. While she has decided to shrug off the inevitable death threats that have followed, she is well aware of the problem. "I don't know if I am scared, but I am worried," she told the Observer as she sat in a bar on Manhattan's Upper West Side.

"At the start I thought it was funny, but now I know that is dangerous... their paranoia works better when they can imagine a devil. Now that devil is me."

For the past three weeks Beck has relentlessly targeted Piven via his television and radio shows as a threat to the American way of life, seizing on an essay that she and her late husband wrote in 1966 as a sort of blueprint for bringing down the American economy.

Called The Weight of the Poor, it advocated signing up so many poor people for welfare payments that the cost would force the government to bring in a policy of a guaranteed income. For Piven, a committed voice of the left, known in academic circles but little recognised outside them, it was just one publication in a lifetime dedicated to political activism and theorising.

For Beck, however, Piven is a direct threat to the US. In show after show, the rightwing commentator has demonised Piven and framed her as part of a decades-old conspiracy to take over the country that culminated in the election of President Barack Obama. Beck's heated language has provoked a tidal wave of death threats against both Piven and her academic colleagues at the City University of New York.

The threats are blunt and – in light of the recent shooting of Arizona congresswoman Gabrielle Giffords – truly frightening. Many appear on Beck's news website, The Blaze. "One shot... one kill," wrote one. Others are sent directly to her email address or those of her colleagues. There are so many that she has contacted the police and this week will ask her college to make a formal complaint to the FBI.

Despite that real security fear, she refuses to back down. Indeed, for someone portrayed as a revolutionary communist, Piven's choice of a meeting place with the Observer was a sly poke back at her critics: a Cuban hangout called Havana Central.

It is typical of Piven. The spry, twinkle-eyed academic pulls no punches when talking of Beck. "He is a very neurotic and peculiar type of person. I don't think he is capable of sane discussion," she said. And his supporters? "They creep me out."

Piven joins a select group on the list of Beck's enemies that includes billionaire financier George Soros, green activist Van Jones and long-dead President Woodrow Wilson. Piven likens Beck to a 21st-century version of Father Charles Coughlin, the 1930s rightwing priest and radio broadcaster who many saw as advocating a US version of fascism. "It is very dangerous. Father Coughlin founded a third political party. Glenn Beck has the Tea Party. We should be worried," she said.

Beck's conspiratorial rhetoric on Fox, which he now often backs with presentations on chalkboards and – in the case of Soros – a puppet show, might seem a bizarre stunt. But it has real-life repercussions. Last year Byron Williams stocked a truck full of guns and bullets with the stated intention of attacking liberal groups in San Francisco that Beck had mentioned. He was stopped by police before he arrived, but in a jailhouse interview Williams hailed the Fox frontman as an inspiration.

"Beck would never say anything about a conspiracy, would never advocate violence. He'll never do anything... of this nature. But he'll give you every ounce of evidence that you could possibly need," Williams said.

That sort of statement is enough to give Piven great concern. "I am teaching a new class soon and I don't know who is going to be in there," she said.

However, at the same time she is excited. Beck's attention has given her a sudden opportunity to air her political views. She has been interviewed by the New York Times, among other major news outlets, and last week she appeared on several television talk shows, including one aired on Fox's rival, cable news channel MSNBC.

Beck has, in a way, achieved what a lifetime of radical activism struggled to do: create a national platform for Piven, who is honorary chair of the Democratic Socialists of America. She wants to put forward leftwing ideas at a time of economic and social crisis in a media landscape that usually ignores them and sees "socialism" as a dirty word.

"This is really an opportunity to rein in Fox News and Glenn Beck. I don't know if it's possible, but I am going to try. It also allows us to assert the value of the politics that we stand for," she said.

It will not be an easy task. Beck has an entire TV network and a global media giant behind him; Piven is an elderly professor. But, for the first time in a long while, she is in demand. "At last now we have a megaphone," she said.