By Daniel Emery
Technology reporter, BBC News
It is estimated that more than a million people died at Auschwitz
The number of hate and terrorist websites has increased by a third in the past year, according to the Simon Wiesenthal Center.
The Los Angeles-based Jewish human rights organisation put the figure at more than 8,000 in its 2008 report Hate 2.0. It said the presence of such sites "demeans and threatens African Americans, Jews, immigrants, gays and virtually every religious denomination".
And the number of so-called hate sites is growing fast, while the use of social networks to push controversial messages is also on the rise.
In May this year, Facebook became embroiled in a row after a number of Holocaust denial groups were set up on the site.
Critics said Facebook was propagating anti-Semitism, others said that free speech was a cornerstone of society and Facebook should keep its hands off.
At the time, Barry Schnitt, a spokesman for Facebook, said it should be "a place where controversial ideas can be discussed".
"The bottom line is that, of course, we abhor Nazi ideals and find Holocaust denial repulsive and ignorant," he said.
"However, we believe people have a right to discuss these ideas."
The Home Office says Don Black's actions could "lead to inter-community violence in the UK".
A few days later, the site had closed two of the groups, Holocaust is a Holohoax and Based on the facts... there was no Holocaust. It said they had breached the firm's terms of service.
But there are still plenty of other Holocaust denial groups on Facebook: Holocaust is a Myth, 6,000,000 for the TRUTH about the Holocaust, The problem of forged Holocaust photos, and Holocaust Deniers, to name just four.
In a visit to the Buchenwald concentration camp in June this year, President Barack Obama criticised Iranian President Mahmoud Ahmadinejad, who had called the Holocaust a "great deception".
"To this day we know there are those who insist the Holocaust never happened, a denial of a fact or truth that is baseless, ignorant and hateful," Mr Obama said in a brief address.
Holocaust denial is illegal in 13 countries, including France, Germany and Israel. It was also a crime in Slovakia, although this law was repealed in May 2005.
The Netherlands, Denmark, Sweden, Italy, and the United Kingdom have all rejected Holocaust denial legislation.
In Europe, citizens are covered by the European Convention on Human Rights which states: "Everyone has the right to freedom of expression."
But it adds that governments can restrict free speech, among other reasons, in the interests of national security, to preserve public safety and for the prevention of disorder or crime.
Rabbi Abraham Cooper, associate dean of the Simon Wiesenthal Center, told the BBC that it was not a freedom of speech issue.
"Holocaust denial is a perfect example of how a hateful idea was incubated on the internet. It promotes hatred, it promotes violence and it's a kind of precursor to genocide.
Some groups advocate direct action against Holocaust denial sites
"It's not the idea that needs to be scrubbed; it's fact that the internet elevates crackpot theories to a level it doesn't deserve.
"These sites aren't about the discussion of ideas; they are about getting people to subscribe to the ideal of hate."
But speaking to the BBC, Douglas Murray, director of think tank The Centre for Social Cohesion, said that society should be able to accept any point of view, even if that view was proven to be false.
"You have to allow different opinions, even lies, as long as they don't incite violence. Otherwise what is true becomes dogma and then becomes incapable of being defended," he said.
In 1995 Don Black founded Stormfront - a white supremacist website seen by many as the internet's first "major hate site", although it had existed as a bulletin board for a number of years prior to that.
In May he was one of 22 individuals excluded from the United Kingdom by the Home Office for "promoting serious criminal activity and fostering hatred that might lead to inter-community violence".
He told the BBC that - in America - people could say and think whatever they liked.
"We believe anyone has the right to discuss the issue [of Holocaust denial] without being censored and, in many cases in Europe, prosecuted and sent to jail.
"It goes beyond censorship on Facebook. We're moving into a new dark age with an orthodoxy in which individuals hold the wrong opinion are prosecuted and in some cases, sent to jail.
"My getting banned from Britain - even though I haven't even tried to visit Britain - is an example," he said.
While the views espoused by Mr Black and others may be offensive to many, in most countries they are perfectly legal.
Mr Murray holds a view that they should remain legal because "in a free society it isn't hard to prove that their point of view is wrong".
Rabbi Cooper disagrees, saying that while you will never keep any idea off the internet, there was no obligation for private companies - such as Facebook, MySpace etc - to carry so-called hate groups; failing that the centre advocates more "direct action".
"We've gone from one problem group back in 1995, Stormfront, to over 10,000," he said.
One group that does carry out direct action on occasion is the Jewish Internet Defense Force, a group that claims it "leads the fight against anti-Semitism and terrorism on the web". It is said that the JIDF has seized control of and deleted Facebook groups deemed to be anti-Semetic or anti-Israel.
In an e-mail exchange with the group's spokesman, "David", the BBC asked why they took such issue with Holocaust denial.
"Holocaust denial is hate speech. It is an attempt by anti-Semites to make Jews appear to be liars and manipulators, those who accept the historical truth of the Holocaust to be dupes, absolve Nazis and their active and passive accomplices of guilt, and so rehabilitate anti-Semitic ideologies," he wrote.
Critics say the internet has enabled alleged anti-Semites to reach an audience of millions.
"Facebook staff themselves seem very torn about these issues and wish to consider a lot of hateful ideologies as 'legitimate political discourse'.
"However, if they are going to take down KKK (Ku Klux Klan) pages and pages which promote Islamic terrorism, then they should also take down hateful Holocaust denial pages and stop pushing the myth that they are for 'free speech'."
He added the group would "do everything in our power" to convince Facebook to "do the right thing".
But Mr Murray said that the grounds for freedom of speech were already laid out.
"If someone thinks they are better because of the colour of their skin, their religion or where they were born, well it's irrational and deeply hateful, but unless they say you should do violence, then I'm afraid we have to accept there are people who have unpleasant opinions."