We have learned a great deal in recent years about reading Horace's satires; there is now widespread agreement that the speaker of the satires is himself a character within them, a persona. Such a persona may be most effective when it has obvious connections with its creator, but that fact does not preclude the exaggeration of reality, or even its complete inversion. For Horace the implications of this approach are exciting: instead of a poet discoursing with cheerful earnestness on morality, on poetry and on his daily life, we have a fictional character, whom we do not have to take seriously at all.
The three diatribe satires present us with a character so absurd that they have been taken, I think rightly, as parodies. Although the poems were once appreciated as effective moralising sermons, even their admirers found it hard to justify the lack of intellectual coherence, to say nothing of the astonishing vulgarity of the second satire. As parodies, however, the poems are wonderfully successful. The speaker trots out a series of banalities: ‘people should be content with who they are’; ‘people should not go to extremes’; ‘people should be consistent’. But he invariably gets distracted, goes off on tangential rants, and makes a fool of himself. The moralist of the first three satires is, to put it bluntly, a jerk.
"The Epicurean Parasite: Horace, "Satires" 1.1-3".