Like a lot of issues you'll likely need to choose a Schelling point (arbitrary cutoff). Some of it is simple inconveniences. It is a lot harder to learn enough psychology, understand your audience, and so on to influence them in comparison to having a program that scans every word they've put on their [social media account here] to decide how best to convince them. That would likely stop a good amount of actors.

If a quite small amount of people had access to and were using the printing press, then that might legitimately be an argument for the government in that country to ban it as it gives them more power over others. Though, once it becomes common and non-secret technology then everyone has been amplified the same way. Now, that 'give everyone the ability to use machine learning to tailor their text to the audience' could be a route your could attempt, but I don't think it makes as much sense for machine learning even if I could imagine a society that has that.