The Romans weren't the only people in Italy; they fought against the Etruscans (who I understand are not considered 'properly 'Italic), Samnites, Sabines, Latins...before actually controlling all - or at least most- of it.
These people seem to have been assimilated, intermarried with 'original' Romans (and I think some eventually got full citisenship) and so on.
What I want to know is - what did the Romans think of these former rivals for control of Italy and, specifically, of Romans who had ancestors from them? Especially for nobles/equites/patricians.
I understand the Romans weren't really racist as a rule (at least, not like we use the word today), but I would expect them to look down on nobles who married foreigners...however, since we are talking about people who were somewhat close geographically if not culturally, how did it work?
The one specific case I can think of is reading that Maecenas - Virgil's patron - prided himself on his noble etruscan ancesty.
I am not surprised by this, as Rome had some Etruscan kings early on and Etruscan civilization seems to have been a MASSIVE influence on Rome (maybe the biggest cultural influence after Greece?), so I guess they had a lot of respect for them.
And I suppose the legend involving the kidnapping of the Sabine women would also make that a 'respected' people (since they are supposed to share ancestry). And speaking of legends, there's also Aenas marrying a Latin princess.
But what about other people from Italy? Are there cases where a Roman noble was insulted or shamed by people bringing up that he had Italian, but non-Roman ancestors? Or, like in Maecenas' case , it was something you didn't have to hide and could even be proud of in some cases?
What period are we talking about? You reference Maecenas, so I'm guessing Augustan period.
By then Italians had legally been integrated into the citizenship for a couple generations, although accomplishing that de facto took more time. There's lots of scholarship out there (I know because I'm the idiot that decided to write a dissertation on Italians in the Roman empire), and they don't always agree. There are a bunch of scholars like Davies, Mouritsen, and Keaveney who tackle Italian integration; these guys take what I call an "historical" (not the best term, but run with it) approach; they come up with different reasons for the Social War which led to integration with Rome (Mouritsen is interesting in pushing the goal of the war as the destruction of Rome rather than participation in Roman empire), but all of them treat the matter in more-or-less legal terms and although they come up with different dates the argument in general runs along some form of sometime in the first half of the first century BCE Romans stopped caring about ethnic distinctions as a factor in determining who deserves access to Roman citizenship. Cicero's "duae patriae" - two fatherlands - tends to be accepted as the complete formation of this idea: every Roman has two fatherlands, one in which he was born owed filial duties and one in which he was a citizen and owed political duties. Some people see this repeated in Augustus' formation of the notion of tota Italia - all Italy - in the Res Gestae. I don't have Mouritsen on hand (I should, but some jerk recalled it), but I think he argues that Romans of the Augustan period showed no interest in the history of free Italian cities.
There's another set of scholars - these include Lomas, Dench, Bradley, Williams - that are more interested in identity formation than legal status; these guys do find Romans discussing ethnic identity being a factor Romans deployed for their own purposes in the late Republic and early Empire. Some of this shows up pretty easily in the sources - the Julians, for instance, played up their ancestors, kings of Alba Longa, that connected them to the Trojans and ultimately to Venus, according to Hesiod one of the older divinities. The Claudians played to their supposed Sabine origins. These guys weren't making the argument that they were something other than Roman; they were arguing that they were Roman AND something else. The Sabines are an interesting case (and Farney's 2007 book is probably the place to go for this). By the Augustan period the Sabines have become mythologized into a people of almost Spartan morality. Making claims to having a Sabine background had implications for your moral character.
And it's not just politicians making these sorts of claims. Livy is proud enough of being from Padua that he sets up Padua as a potential rival of Rome for Empire. Asinius Pollio and Velleius Paterculus were both proud of their ancestors who fought in the Social War and made no effort to disguise their ancestry. There are even cases in which Farney suspects Romans - using names like Sabinus and such - were attempting to pass as coming from a particular background to which they didn't belong, because of the favorable stereotypes associated with those backgrounds.
And to finish up; about that Etruscan kingship you mentioned. Some people (Cicero and Dionysius of Halicarnassus come immediately to mind) go out of their way to point out Tarquin Priscus wasn't Etruscan, but a Greek refugee from Corinth who arrived at Rome via Etruria and changed his name (often given as Lucomo originally) to better assimilate into Italian and Roman cultures. I haven't seen a convincing argument about what exactly the ideological payoff of this move is. If I figure it out you can read the publication.