It's not even a problem of fiction or lies. AIs don't care about truth. They exist orthogonally to truth. They're just averaging a large body of text. If fascists had a consistent narrative and worldview, then this wouldn't be a problem. If they all devoutedly followed the same religion, and defined their whole worldview accordingly, then an AI could be trained on that religion. And it would never stray from orthodoxy. AIs don't know truth; they only know their training data. And as long as you have a large volume of consistent training data, you can train them to repeat anything.
The problem for fascist LLMs is that fascism isn't consistent through time. It's the Orwellian "we've always been at war with East Asia" factor in play. Fascists don't even try to be internally consistent. What was party orthodoxy today can be unforgivable heresy tomorrow. And AIs just can't keep up with what is supposed to be the story this week. Human fascists can handle that kind of rapid heel-turn. LLMs can't. Once they're trained; they're trained. If you want them to be up-to-date on the latest party lies, you have to be continuously training new versions of the fascist LLM.
You can't train LLMs to be fascist beyond just very general traits like having overt racial prejudice. But even that's not always useful, as fascists are inconsistent about what racial groups are deserving of annihilation from one week to the next.
So it's not so much that fascist AIs fail because of reality's liberal bias. It's that fascists don't believe in a consistent version of reality. And without that, LLMs just can't keep up with the whirlwind of lies.