In these days when we get so much of our information from the internet, we need to be sensitive to how much manipulation of it can occur. While some of this is done by individuals, this Intercept article from 2014 based on information contained in the trove of secret documents released by Edward Snowden shows that government agencies, in particular the GCHQ (the UK’s intelligence arm), resort to all manner of dirty tricks to destroy the reputations of people and disrupt groups that merely oppose government policies and actions, even if they have never been convicted of any crime nor had any connection to any terrorist activity. The ostensible mission of these government agencies is to monitor terrorist activities not legitimate political activism that happens to be against government policies.

In monitoring, infiltrating, and disrupting the work of these groups, these government intelligence agencies draw upon research in the social sciences.

Among the core self-identified purposes of JTRIG are two tactics: (1) to inject all sorts of false material onto the internet in order to destroy the reputation of its targets; and (2) to use social sciences and other techniques to manipulate online discourse and activism to generate outcomes it considers desirable. To see how extremist these programs are, just consider the tactics they boast of using to achieve those ends: “false flag operations” (posting material to the internet and falsely attributing it to someone else), fake victim blog posts (pretending to be a victim of the individual whose reputation they want to destroy), and posting “negative information” on various forums.
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Critically, the “targets” for this deceit and reputation-destruction extend far beyond the customary roster of normal spycraft: hostile nations and their leaders, military agencies, and intelligence services. In fact, the discussion of many of these techniques occurs in the context of using them in lieu of “traditional law enforcement” against people suspected (but not charged or convicted) of ordinary crimes or, more broadly still, “hacktivism”, meaning those who use online protest activity for political ends.
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The broader point is that, far beyond hacktivists, these surveillance agencies have vested themselves with the power to deliberately ruin people’s reputations and disrupt their online political activity even though they’ve been charged with no crimes, and even though their actions have no conceivable connection to terrorism or even national security threats.

Individuals and private groups are capable of using the internet to cause harm to the reputations of others. But when governments get into that business, they can do much greater damage because they have so much information about us at their fingertips and have a vast amount of resources at their disposal with which to spread false information.