I am reading a recent-ish book on Greco-Roman history where the author makes a couple short remarks along the lines of (translated) "The Germanic conquerors themselves also kept a racial distance from the Roman citizens and emphasized their own racial superiority." Now, I can assume that "race" here is being used in a contemporary rather than modern sense, in the way that e.g. Tacitus would describe the Germans as a distinct ethnicity and culture. However, that still sounds surprising to me. Due to being basically a primer on all things Greco-Roman, the book obviously summarizes a lot, and does not really elaborate on this particular point.
So, did the Late Antique Germans of Theodoric et al. really see themselves as "racially" superior to the Romans they had conquered, in such a way that they'd try to avoid intermarriage for genetic or cultural rather than simply political reasons? Distinct from the way that the Romans (or basically anyone else) saw themselves as superior to people they conquered? And if yes, were those perceived racial traits just the same "tall, strong and rugged" stuff that the Romans themselves mentioned, or something different/more elaborate?
For what it's worth, the author mentions in a condemning tone that the Antique Germans' belief in their racial superiority would come back to fuel 19th-century ideas along the same lines, so I expect him to be critical on the subject – but he still depicts it as a fact that said beliefs existed at the time.
It's not possible to answer this question for many Germanic groups, but the Ostrogoths in Italy seem to have left enough evidence to suggest they were a distinct if not discrete group but this was not based on superiority. At least in the earlier part of Theoderic's reign the Ostrogoths seem to have treated themselves as a separate military caste, part of society but not integrated into it. So they had their own church, seemingly lived in separate areas of towns and had different laws applying to them.
However, they were not biologically exclusive. It seems they would integrate children of Roman aristocrats, and within the ranks of the Goths were sub-groups with distinct ethnic identities such as Rugians or Heruls.
In fact this separate military caste was the norm for fifth-century Roman society, where emperors tried to enforce rules that sons followed their father's trade. This was particularly the case for the army where trained manpower was always needed (hence Theoderic and his followers technically being an imperial army when they invaded Italy). The military had always had their own religious ceremonies and the like as well, so even the Gothic church was not an innovation as such. That the army in Italy took on an explicitly non-Roman identity was fairly new (although the Franks seem to be linked to the army in northern Gaul) but that it still acted as the protector of a somewhat-detached civilian society was not.
A writer interpreting this as racial superiority is either very old fashioned or projecting modern concerns onto history. The Goths were separate and elitist but they weren't basing their identity around ethnic identification so much as (male) military participation. In some ways this is closer to the free Spartans than the Nazis. We can't be so certain for other Germanic groups (there's nothing to say the Anglo-Saxons didn't seem to exterminate the Britons in many places for example) but what evidence we do have can certainly support a model of a military elite, with varying degrees of integration with local societies.