Cicero was a conservative in some ways. But I don't think he was particularly prejudiced or classist, for the time. Remember that he was technically a plebeian himself, although obviously a privileged and successful one.
The important point is that no one should mistake the equestrians for anything close to even the top end of the middle class.
However, the Senatorial class was not an economic distinction either but rather an aristocracy. Even in the Late Republic these were old families who had had Senators and Consuls in their heredity. There were fewer of these clans, 14 at the time of Caesar (of the Julii clan). Cicero by comparison was of Equestrian rank and a New Man, novus homo, in the Roman political world.
Equestrians weren't knights anymore, expected to field a horse, .... The Roman legions had been professionalized by then. There were property and suitability requirements enforced by the Censors.
The Equites were purely a social/wealth based class, any Roman citizen could become one if he we satisfied the wealth requirements.