It was audacious of Horace to include in his poem even so glancing an allusion to Rome's own recent civil wars, during which many poor men — Horace included — had trembled at the arms of the soldiery, and during which the better qualities of men, which wine was given to commemorate, had been so smothered. After the death of Caesar, Horace had enlisted under the tyrannicide Brutus, and had served him as a staff officer ("tribunus militum"). But he survived the battle of Philippi only by discarding his shield and running away. Under the principate of Augustus he was given a comfortable job in the treasury as a scribe, which allowed him time to pursue poetry. He was protected and pampered under the new regime. Maecenas, Augustus's favourite and chief counsellor, gave Horace the Sabine farm he commemorates in his poetry. 

Even so, it is interesting to speculate on how Augustus — himself no king,  of course — might have responded to these republican touches. Would he have been nettled by Horace's attachment to the old political dispensation? Or, given his political subtlety, would he have been gratified that his principate had fastened its grip on Rome so stealthily that even such potentially seditious memories might be expressed?