The recent terror attacks in Paris have unleashed a barrage of anti-Muslim and anti-immigrant comments on the Facebook pages of federal politicians and their parties in Canada — much of it plainly visible to the public.

Managing racist, sexist, homophobic and harassing material is just one of the new challenges facing parties who want to have an active social media presence, grounded in the concept of free speech and open dialogue.

A Jan. 7 post on Stephen Harper's Facebook account, in which the prime minister said he was "horrified by the barbaric attacks in France," received approximately 575 comments. Some six dozen — expressing support for blocking immigration from Islamic countries, closing Canada's borders or just criticizing Islam — were still on the page more than two weeks later.

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"Time to step down on all Islamic communities worldwide," wrote one visitor to the page.

Said another: "All muslims should go home and never be let back here please mr harper make that happen they steal real peoples jobs that belong to us canadians."

A Jan. 14 Conservative Party of Canada Facebook post entitled "Protecting Canadians from Barbaric Cultural Practices" — aimed at promoting the government's legislation barring forced or child marriages — elicited similar sentiments.

One example: "Deport them all if you want to save Canada."

A handful of other comments were taken down after The Canadian Press asked the party last Tuesday about their Facebook policy.

A few commenters expressed dismay with the vitriol against Muslims.

"Wow ... so much hate, bigotry and fear mongering on this page! So sad to see that so many in Canada have been brainwashed to think like this," said one.

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Harper's Facebook presence is described on the site as a "family-friendly page," which notes that the administrators reserve the right to delete inappropriate submissions including hateful, malicious, uncivil or disrespectful content.

Party spokesman Cory Hann explained that an online Facebook tool is used to screen out certain words, but the rest of the work falls to a party staff member who must scan the content manually.

"With over 100,000 fans of our Facebook page, we do our best to keep up with the large volume of comments we get daily," Mr. Hann said.

"Obviously it goes without saying we don't endorse every single comment, and work to remove inappropriate ones that the built-in filter does not pick up."

Facebook pages for NDP Leader Tom Mulcair and Liberal Leader Justin Trudeau relating to the Paris attacks also included a sprinkling of comments critical of immigration from Muslim countries, all of them along similar lines.

Both the NDP and the Liberals also have a policy against hate speech and racist comments on their Facebook pages.

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Privately, party insiders say keeping up with the sheer volume of comments can be difficult, given that staff are also taking care of a range of other tasks.

Ian Capstick, managing partner of public relations firm MediaStyle, said major corporations will purchase a separate filtering program from Facebook's, plus hire staff or an outside firm to keep up with the comments.

Mr. Capstick, a former Parliament Hill aide to NDP and Liberal politicians, says the real source of the problem for Canada's political parties is they still only see social media as a one-way conversation.

"Canadian politicians are very good at using social media to broadcast, but they're very bad at using it to have actual conversations," said Capstick, whose firm does some social media management.

"If there were more actual conversations going on, there would be more regular usage of those Facebook sites and Twitter accounts, and people would be cleaning them more regularly."

The media industry has also grappled with the challenge of policing comments sections, and the racist, sexist or homophobic comments that can live there. Last year, the Chicago Sun-Times took down its comments sections in order to study the issue, while other sites have played down the sections.

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Paula Todd, digital media professor and author of "Extreme Mean: Trolls, Bullies and Predators Online," said some offensive speech should be left online so that it can be exposed and critiqued by others.

But Ms. Todd, the chair of the digital issues committee at Canadian Journalists for Free Expression, said political parties have an obligation to ensure sites they're responsible for do not contain examples of hate speech.

The Criminal Code's section on the "wilful incitement of hatred" describes a perpetrator as someone who "wilfully promotes hatred against any identifiable group." Such groups are defined by colour, race, religion, ethnic origin or sexual orientation.

"We're discovering the effects of putting all this horrible stuff online," said Ms. Todd.

"One of the effects is that because it's 24 hours a day, because it flies around the world in seconds, and because it's permanent, these kinds of hate attacks can be more damaging than just the face to face."