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Few US presidential candidates have been disliked as much as Donald Trump and Hillary Clinton. But attacks on Clinton in particular have sometimes crossed a line, displaying open hatred. Why?

Emily Longworth, 25, grew up in the southern state of Georgia discussing politics around the dinner table with her father and grandfather, both staunch conservatives.

Working as a weapons repair specialist in the US military, she had to be careful what she said about America's politicians.

But since leaving the military for an office job three years ago, she doesn't hold back - especially when it comes to Hillary Clinton.

"She is a lying, manipulative, narcissistic woman who deserves nothing except to be put in jail for life," she says.

Media playback is unsupported on your device Media caption Emily Longworth: It may be unjustifiable with other people - it's not with us

Longworth's expletive-laden tirades have been attracting hundreds of thousands of viewers on Facebook and YouTube.

In one video, addressing Clinton and her "diehard feminist Nazi fans", Longworth describes her "disgust" at having to listen to "that painful scratching noise that you like to call intelligence spew from your mouth like typical Clinton diarrhoea".

She is also spokesperson for a group that sells T-shirts and merchandise carrying the slogan "Hillary for prison" - Clinton deserves a prison sentence, they argue, for episodes such as the Whitewater property controversy in the 1990s, the deadly attack on the US diplomatic compound in Benghazi in 2012 while she was secretary of state, and her use of a private email server while in office.

Clinton is also attacked for being a woman, and Trump is not attacked for being a man Jennifer Mercieca, Historian of political rhetoric

Many Americans might agree that Clinton - the first female nominee for president from a major political party - is tainted by her role in these controversies, and this may help explain her unfavourability rating of more than 50%.

But most critics would not resort to the kind of extreme language that has seen Longworth blocked by Facebook for repeatedly violating its "community standards".

So why does she do it?

"If you have controversy… you strike conversation," she says.

"Unfortunately, it's the way society works… You do strike up conflict, but it promotes business and promotes the cause.

"This may be rash and unjustifiable with other people. It's not with us."

Longworth is part of a small but noisy radical tendency on the fringes of the Republican Party.

At Trump rallies, pockets of supporters shout "Lock her up!"

Some wear T-shirts saying "Trump that Bitch", and there are those who describe Clinton as "the servant of Satan" or use hashtags such as #Killary on social media.

Image copyright AFP Image caption Campaigning in Philadelphia on Monday, Trump clapped along as supporters chanted "Lock her up!"

Trump is also the focus of contempt, and worse - he's been likened to Adolf Hitler and accused of having a personality disorder.

"I've seen both candidates attacked based upon physical characteristics, both attacked based upon personality traits, both attacked based on past decisions," says Jennifer Mercieca, a historian of American political rhetoric.

"The one element that separates that two is that Clinton is also attacked for being a woman, and Trump is not attacked for being a man.

"Perhaps, since she is the first female presidential candidate, people are ill-equipped to criticise her about anything else, or in any other way, than via gendered and misogynistic slurs."

Misogyny can be obvious, she says - as in the use of the word "bitch" - or it can be hidden.

Image copyright Reuters

Many of the barbs directed at Clinton revolve around her husband's well-publicised sexual transgressions in the 1980s and 90s.

She orchestrated all of this! She used his addiction to make him dependent upon her! Dinesh D'Souza, Conservative writer

Last year, Trump himself retweeted the comment, "If Clinton can't satisfy her husband, what makes her think she can satisfy America?" though he later deleted it.

But some critics focus on her alleged role in the scandal, as a co-ordinator of attempts to keep the women involved quiet and to blacken their character.

In a recent film, Hillary's America: The Secret History of the Democratic Party - the top-grossing documentary in the US this year - conservative writer Dinesh D'Souza even argues that Hillary Clinton encouraged her husband to sleep with other women.

"She orchestrated all of this!" he says, in the film's narration. "She used his addiction to make him dependent upon her!"

This attack and others like it show a determination to cast Clinton as a "co-perpetrator" in her husband's wrongdoings, says columnist and author Michelle Goldberg.

"It also reinforces the idea that she is so power-crazed that she's unmoved by normal human drives like love, loyalty and jealousy."

Image copyright Getty Images

In the decades that the Clintons have been in the public eye, US politics has become increasingly polarised - a process partly fuelled by the proliferation of radical voices on talk radio and the internet. The election of Barack Obama - the first black president, and one of the most liberal for decades - also proved to be a red rag to some, including D'Souza.

In one of a series of controversial books and films, the man described in the liberal media as "America's premiere conservative troll" argues that the president wants America to be "downsized" as punishment for the "sins of colonialism".

In his latest film - alluding to the Clintons' ability to turn political success to financial advantage - he goes so far as to accuse Clinton of being a gangster who plans to "steal America".

She's a creep, she's a witch, she's turned over to evil Alex Jones, Radio host

But Donald Trump himself has also done much to put about conspiracy theories regarded by many commentators as devices to whip up hostility towards Obama and Clinton.

He began his journey to the Republican nomination by reviving the long-debunked "birther" claim that Obama was not born in the US and is therefore ineligible to be president, only to disavow it last month.

He has warned the November election could be "rigged" in Clinton's favour, and alleged that Clinton and Obama were co-founders of the so-called Islamic State group.

Obama, he has long suggested, is Muslim, and in Sunday's debate he referred to Clinton, not for the first time, as "the devil".

According to Alexander Zaitchik, author of Gilded Rage: A Wild Ride Through Donald Trump's America, Trump's candidacy has made conspiracy theories "shockingly accepted" among people who believe mainstream politics has failed.

"He's promoting stuff that never would have been promoted up until now by the Republican Party," Zaitchik says.

Of all the Hillary haters, one of the most vitriolic is Texan radio host and Trump supporter Alex Jones, described by the Southern Poverty Law Center as "the most prolific conspiracy theorist in contemporary America".

The 9/11 attacks and the Boston Marathon bombings were, in his view, plots staged by the government.

Image copyright Reuters Image caption Alex Jones spoke during a rally in support of Donald Trump near the Republican National Convention in Cleveland

In a shouty performance on the BBC's Sunday Politics in 2013 he reduced host Andrew Neil to twirling a finger around his temple, saying, "We have an idiot on the show today."

But his programme, the Alex Jones Show, and his InfoWars website attract an audience of millions across the US.

When we treat politics like sport or war, then we treat ourselves as fans or soldiers, cheering or booing or following orders Jennifer Mercieca, Historian of political rhetoric

"She's a creep, she's a witch, she's turned over to evil," Jones said, referring to Clinton, in a special broadcast during the Democratic Party convention.

"Look at her face… All she needs is green skin."

During the same show, Jones played a video comparing the former first lady's laugh to a hyena.

Posted on the internet by a comedy network, the video had been taken down after complaints.

But if some found it entertaining, Goldberg says mockery of Clinton's appearance and her laugh represent "misogyny at its most elemental".

Harsh attacks on Clinton have not been confined to the right-wing.

In a bruising primary campaign against rival Bernie Sanders, she also made enemies on the left, one of whom, Andrew Levine, a Senior Scholar at the Institute for Policy Studies, told the BBC he would "swim through vomit" before voting for her.

In Mercieca's view, the rhetoric of this election has gone dangerously far.

"When we treat politics like sport or war, then we treat ourselves as fans or soldiers, cheering or booing or following orders," she says.

"When we treat politics like that, then those who hold differing views from us are not wrong, they are evil. They are not mistaken, they are enemies."

Clinton's comebacks to criticism

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Benghazi attack: Clinton has said she takes responsibility for the attack on the US mission that killed four Americans in 2012. Several congressional hearings have failed to prove wrongdoing on her part

Clinton has said she takes responsibility for the attack on the US mission that killed four Americans in 2012. Several congressional hearings have failed to prove wrongdoing on her part Use of a private email server: An FBI investigation concluded that no "reasonable prosecutor" would bring a criminal case against Clinton, but that she and her aides were "extremely careless" in their handling of classified information

An FBI investigation concluded that no "reasonable prosecutor" would bring a criminal case against Clinton, but that she and her aides were "extremely careless" in their handling of classified information Clinton Foundation: Questions over potentially inappropriate relations with wealthy foreign officials and businesses have proved fertile ground for Trump, but Clinton's campaign has pointed out he, too, was a Clinton Foundation donor. Clinton herself has stressed the lifesaving work of the organisation and denied allegations of corruption

Questions over potentially inappropriate relations with wealthy foreign officials and businesses have proved fertile ground for Trump, but Clinton's campaign has pointed out he, too, was a Clinton Foundation donor. Clinton herself has stressed the lifesaving work of the organisation and denied allegations of corruption Sex scandals: Donald Trump has brought women who accuse Bill Clinton of sexual assault - including Juanita Broaddrick who claims he raped her - to the forefront of his campaign. The Clintons have insisted the allegations are baseless, though the former president has acknowledged consensual affairs

Read more:

Clinton's 'emailgate' diced and sliced

Why is Clinton's foundation so controversial?

Katty Kay: Hillary's campaign and Bill's women

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