Author Naomi Wolf suggests footage of hostages being beheaded by ISIS militants isn't real.
The 51-year-old Jewish American writer made a series of controversial statements questioning the authenticity of the footage in a number of messages on her Facebook page.
The initial post in which the feminist activist questions where the terror group are 'getting all these folks from' was deleted.
In another post, she also said that the Obama administration was sending troops to West Africa to confront the Ebola outbreak so they could return with the deadly infection - justifying a military takeover of Africa.
Social media users quickly rounded on her with some suggesting her theories were 'crazy' while others said her views were 'harmful' and had disrespected the victims' families.
A video released on Friday appeared to show British hostage Alan Henning being beheaded by Jihadi John.
He is the fourth person to have been brutally murdered at the hands of the extremists, and a fifth, former Army ranger Peter Kaggis, has been threatened as the next victim.
After making the controversial statements over the weekend, Wolf defended her actions saying she was criticizing the reporting of the story - suggesting the video had not been properly confirmed by two sources.
The post, that was later taken down, said: 'OK two of the hostages just happened to go from long careers into the military to... sudden humanitarian work (same was true of the latest British hostage). Where are they getting all these folks from?
'If someone is abducted there is a record with Amnesty and with Reporters without Borders. Can someone please confirm that these organizations have any record of this person having been abducted?
'The NYT (New York Times) yesterday ran a depressingly sloppy editorial claiming that all the ISIS beheading videos must be real because 'there are so many of them on youtube'.
'THAT's journalism? They also called ISIS 'evil' many times - which is not langauge of a news analysis, it is a theological category for some faiths and a Global War on Terror talking point... this may all be true but it takes five people to stage an event like this - two to be 'parents' - two to pose for the cameras... one in a ninja outfit... and one to contact the media that does not bother checking who ANY of these four other people are...'
During the social media backlash, Mark Boothroyd said: 'Don't insult these people who have given their lives for humanitarian work.
'The activities of all these people have been well documented over the years. They are known people with families and friends who have supported them. Stop spreading conspiracy theories.'
In her most recent post, the author has said that she stands by what she wrote