I'm guessing head-canon also counts for this thread? If so, here's some of mine:
The enjoyment from being petted shared by most if not all ausar is physical in nature; it's kind of like sexual stimulation, but without any inherent sexiness (so it's fine to do it to kids). Furthermore, the ausar have known about this since before they even invented writing. Or civilisation. Or agriculture. (There's ancient cave paintings that clearly depict ausar petting each other.)
Despite having no fewer than two distinct member races, the Gryvain Heartland Republic never had any anti-racism laws until after it made First Contact with the UGC. To be fair, anti-discrimination principles were so ingrained to the GHR's culture that such laws were effectively unnecessary.
Because its homeworld is basically space-Australia (specifically, space-Outback; a giant desert where everything's trying to kill you), Ausari society is much less fond of nature than Terran societies. As a result:
- Ausaril is named after the ausar; it's effectively saying the planet belongs to them (in the possessive sense) and not the other way around.
- They've managed to cause less environmental destruction than us because Ausaril has less environment to destroy than Earth.
- Non-sapient animals are, without exception, considered objectively inferior to all sapients. This, in turn, has two results:
- The concept of keeping animals as pets never really occurred to the ausar until humans introduced it to them. Prior to this, all domesticated animals were either livestock or beasts of burden.
- Ausari culture views furries* as either willingly bringing themselves down to the level of non-sapient animals, or elevating those animals to the same level as sapients. Either way, it explains why Ausari culture hates furries*.
*Does not include races like kui-tan or milodan since they're naturally-occurring.
The "kaithrit love milk" stereotype actually has some basis in their biology; lactose tolerance is naturally present in all kaithrit, and their tongues even have lactose-specific receptors that react in a similar but distinct manner to sweet-taste receptors.
Unlike the above point, the "ausar and kaithrit hate each other" stereotype is due almost entirely to the Terran "cats and dogs hate each other" stereotype. There was probably some incident (maybe an early border dispute?) that caused Roshan society to develop a negative opinion of the ausar, but that opinion isn't shared by kaithrit from outside kaithrit-dominated space (or even some planets within said space), and ausar-dominated societies don't treat kaithrit any differently from other humanoid non-ausar (and many ausar-dominated worlds, including Ausaril, also have not-insignificant kaithrit populations without any issues whatsoever).
The GHR is so widely-loved in the UGC that no-one would dare declare war on them out of fear of retaliation from the rest of the UGC. Similarly, if the GHR were to ever declare war themselves, most of the rest of the UGC would follow suit as soon as they've picked up their jaws (or equivalent anatomical structure) from the floor.