Someone looking to organize a trade union in her workplace? Anonymously load AI videos of that person jerking off in public or some other thing that would shatter their reputation, or worse have them confessing to crimes.
Its honestly worrying.
The former is more effective. The latter won't get very far if you deny it and stick to your story.
Most modern psyops avoid the legal system since there are actual consequences for lying. Before social media, public trials were the only way to get enough national attention to defame someone, which required putting some skin in the game. Now you can just tell your "truth" on social media and the accusation is as good as a conviction. Faith-based systems are easily exploited.
Cryptographically signing the news might be necessary, but it sure won't be sufficient, as your local government can pretty directly tell people who the trustworthy news sources are/which signatures they should trust. You need more than just the technology to solve problems like this.