Launching a Strategy and Plan of Action on Hate Speech on Tuesday at the UN, he declared: "Hate speech may have gained a foothold. But it is now on notice, and we will never stop confronting it."
"Hateful and destructive views are enabled and amplified exponentially through digital technology, often targeting women, minorities, and the most vulnerable. Extremists gather online and radicalise new recruits," he said.
He called the "new forms of self-policing by social media platforms and the commitments included in the Christchurch Call" welcome developments. The Christchurch call to eliminate terrorist and violent extremist content online was adopted last month by government and technology leaders in response to the terrorist attack on mosques in the New Zealand capital in March.
Guterres suggested harnessing digital technology "to monitor activity, target our response and build support for counter-narratives".
He added that the "recent emergence of volunteer groups that are organising to counter harassment and hate online shows the potential for collaboration" between them and the UN.
"In both liberal democracies and authoritarian regimes, some political leaders are bringing the hate-fuelled ideas and language of these groups into the mainstream, normalizing them, coarsening the public discourse and weakening the social fabric," he said.
Later while speaking to reporters, he refused to name liberal democracies and political leaders he was referring to. "If I name and shame, the only thing that would be broadcasted would be the naming and shaming, and what I want is the substance of the issue to be dealt with."
He added that it was his strategy to not name or shame any individual and would "go on applying whenever it makes sense".
He said that to follow up the launch of the plan of action, he planned to convene a conference on the role of education in building resilience against hate speech.
He straddled the fine line between freedom of speech and suppression of hate speech ruling out blanket bans on free expression.
"Addressing hate speech does not mean limiting or prohibiting freedom of speech," he said. "It means keeping hate speech from escalating into something more dangerous, particularly incitement to discrimination, hostility and violence, which is prohibited under international law."
"We need to treat hate speech as we treat every malicious act: by condemning it, refusing to amplify it, countering it with the truth, and encouraging the perpetrators to change their behaviour," he added.
He said that his plan would take aim at the root causes of hate speech which include "violence, marginalization, discrimination, poverty, exclusion, inequality, lack of basic education, and weak state institutions" and enable the UN respond to it.
Mentioning "anti-Semitism and anti-Muslim hatred", he said that "around the world, we see a groundswell of xenophobia, racism and intolerance, violent misogyny", and added: "In some places, Christian communities are attacked." There was no specific mention of other religions facing persecution and attacks.
(Arul Louis can be reached at arul.l@.in and followed on Twitter @arulouis)
( With inputs from IANS )