You need to flex your imagination.
A kid fabricates a video implicating his enemy in some crime that would appeal to the barely restrained hatred of internet trolls, a hatred always ready to manifest itself. He recreates the target's bedroom, posters, etc., and makes sure the video finds its way into just the right hands, then riles his audience to a fever pitch. That kid wouldn't even have to be particularly malicious, just ignorant; he probably wouldn't even imagine it ending as badly as it could.
Look, this is no different than any other kind of fraud, except that the apparent solutionâ""internet justice"â"is being lauded instead of being more aptly compared to a crowd of pitchfork-wielding racists (for instance; replace with any non-internet, real-life trolls).