Problem is that they are real citizens. In China, they're referred to as 50 Cent Army (or 50 Cent Party), because that's how much they're believed to be paid for every pro-government post.
Their engagements are usually not. There are botnets upvoting/downvoting/liking/retweeting stuff, but each and every post is written by an actual human, and there are guidelines as to how they need to respond to different stories. It's not like there's one human in charge of posting to 100s of accounts.
So is that underhanded or not? It is not completely different from Amnesty who occasionally sends out emails asking you to sign some list of signatures or to send complaint letters to some third world despot. There are very few rules in this area so it is hard to say what is fair and what isn't. Even if there were, there's no way the rules will be enforced. I'm pretty sure that all these "scandals" are just the tip of the iceberg. The dumb ones are getting caught. More refined state actors (not Russia or China) already have way better methods that Twitter and Facebook can't (or wont!) detect.
Then there's a strong argument to be made that Amnesty gets the moral high ground because their goals are altruistic.
Either way, I think it's an apples to oranges comparison.
* civilian drone-strike killings
* suspension of travel from Muslim-major countries
* attacks on rights of women & girls
* new Guantánamo Bay transfers
* gun violence
* death sentences
https://www.amnesty.org/en/countries/americas/united-states-...
If they aware enough of how horrible their government is that they can ignore what it says and assume it's all a lie, sure.
If the Chinese government has done anything to make citizens trust its authority, such as censorship etc, then the ad is manipulative.
> While the ad was propaganda it wasn't manipulative or underhanded.
Perhaps not in itself, but taking the very example you give, it is manipulative.
Use news stories to paint the "official" picture and use astroturfing to provide a counterpart to the "official" picture. Both as parts in a larger underhanded play.
But what is going on these days is that governments are engaging in propaganda where the identity of the sender is shrouded. For example Twitter accounts controlled by the Chinese state pretending to be common citizens. I think such propaganda is not ok and also that it is not only China and Russia doing it but also Western states and states that are supposed to be friendly to the West.