You think that does not make sense? I'm just trying to create a correct explanation.
However, I do not put him scout enters powerfully into the camp of Caesar, in fact we are in a peaceful manner, as an ambassador who brings gifts from his land (which this case vocabularies on European languages, the Ancient Roman books (of course in English) that Caesar had never seen.
I am sure that Caesar did not consider what happened after the Gens Julia (which became extinct with the suicide of Nero, and that after his death, the legion is likely to escalate as so happens in Rome because of the continuous tyrants Goven did not know anything but following their own selfish whims.
So: the scout does not accuse anyone, but only warns of the danger that lurks behind the choice of Caesar himself.
I think you may be underestimating the Caesar of Fallout. It's quite likely that he is the most classically educated person on the continent. If he had access to a large library, he probably already read the primary sources that your scout thinks he's never seen. Some of those books probably survived the Great War, after all, they had already survived two thousand years and are in every good library in the United States. He has probably already read the books written by the real Caesar, Tacitus, Suetonius, etc... He probably devoured them. He seems to be very familiar with Caesar's "Gallic War" at the very least. He probably already knows what happened in the years after the real Caesar's assassination, and Octavian, and all the Julio-Claudians. The man lectured me on Hegel, for God's sake. It wouldn't surprise me in the least if I found out he had read Gibbon as well.
But the Fallout Legion, for all it's trappings, bears little real resemblance to the actual Roman Empire, and the Fallout Caesar knows he's dying, and for some inexplicable reason has chosen Lanius as his sucessor, rather than the far more Octavian-like Vulpes Inculta. Why? Because he's not the real Caesar, and events in the wasteland will play out far differently from those in the real Rome. The metaphor only goes so far.