This paper comes off as eager to avoid this topic: they (briefly) talk about detecting foreign LLM spam, which is called propaganda, but sidestep the idea of our own side using it. If we were considering talking about that, we wouldn't choose negative-sentiment descriptors like (quoting the paper) "nation-state sponsored propaganda", or "disinformation campaigns"; we'd use our own netural-sentiment jargon, which is "psychological operations" ("psyops") [0].
That we're not widely debating this question right now *probably* means it's far too late to have a chance of stopping it.
edit: Or, to rephrase this as a question: Is it ethical to spam another democracy with millions of chatbots pretending to be citizens of that country—if the effect is to manipulate those citizens to not go to war with our own side, saving our own lives? Is that an atrocity or is that legitimate warfare?
[0] https://en.wikipedia.org/wiki/Psychological_operations_(Unit...