Although the Eastern Roman Empire lasted far longer than the West did, any literate man in the Empire was almost certain to know the origin of the Romans was from the Italian Peninsiila rather than the Hills of Thrace. How did the Romans reconcile this history with their Eastern Greek Empire as opposed to the Western Latin Empire which had been dissolved since the times of Emperor Zeno? Especially after the Fourth Crusade.
This is a very interesting question that deserves to be answered. Sadly, the topic is somewhat outside my area of expertise. A couple of years ago I took a class on the history of the crusades and as a part of it I wrote an essay on Byzantine views on the crusaders (and, tangentially, the latin west). It covers the period of circa 1000-1204 and as such does not consider the sack of Constantinople. Nor does it focus on the Byzantine identity as Romans (although they did very much identify themselves as such). However, seeing as this question remains unanswered for now, I hope that by posting parts of my essay here it may give you at least some idea of how the Byzantines viewed westerners in general. If it is deemed too off topic by the moderatii then I apologize. The excerpts of my essay cover two important aspects: religious views and social/cultural perspectives (the original text included a third part on political attitudes but it has been excluded from this post).
Religious differences and Byzantine views on Catholicism
There has been a tendency in scholarly writing about the relationship between the Byzantine Empire and the crusaders to emphasize differences and to portray the two groups as essential opposites. This is of course an oversimplification which I will show later in this text. Yet there were some concrete and meaningful differences between the Byzantine Orthodoxy and Western Catholicism that are worth mentioning. I will however not be discussing the question of papal primacy in this essay, even though this was the second most important disagreement between the two churches, instead I wish to focus on some of the doctrinal differences that existed.
A very important doctrinal difference revolved around the type of bread that was used in the Eucharist. During the 11th century complaints about the use of so called unleavened bread (or azymes) in the Eucharist become quite prolific. The reason that unleavened bread became such an important religious matter during this time is, according to Tia M. Kolbaba, that it came to signify what it meant to be Orthodox and Byzantine or “Roman”. During the first half of the 11th century conflicts with Jews and Armenians who used unleavened bread had become permeated with this issue of Orthodox identity and when the Byzantines learned that the Latins also used unleavened bread it was not a great leap to consider them heretical like the Armenians and Jews whom they had already been in conflict with regarding this matter. Although it is very important to note that not all Orthodox churchmen considered Latins or others that used azymes to be heretics. A theme that runs throughout this essay is the fact that there was never a singular or unanimous Byzantine perspective on any particular issue but rather many different views and opinions.
Another point of dispute regards the so called “Filioque”. That is the addition of “and from the son” to the Niceno-Constantinopolitan Creed that altered the procession of the Holy Spirit. Those Byzantines that maintained that this alteration was a heresy could draw support from the Patriarch Photias who as early as during the 9th century had criticized the Westerners for adhering to this, in his opinion, false Creed. The Komnenian period (1081-1204) saw a renewal of arguments against the Filioque that repeated much of Photias sentiments two centuries earlier.
The last difference I want to draw attention to concerns holy war. The Byzantines vehemently rejected both the Muslim concept of Jihad and the Christian notion of crusading. The Byzantines did not have a concept of holy war (though they referred to the ancient wars for control of the Oracle at Delphi as such). Yet you could say that all wars that the Byzantines fought were holy because the Emperor, who declared them, was holy. This is of course a matter of how you define the term "holy war". George T. Dennis makes an interesting distinction between holy wars and religious wars. In order to determine if a war is religious or holy one should ask if the belligerents were fighting mainly for religious reasons or not. If they did, as in the case of the crusades, they were fighting a holy war. If they were merely using religion as a motive among others – then the conflict should rather be defined as a religious war. With Dennis' distinction in mind, the Byzantines did not fight holy wars in this sense. The Byzantine church, unlike its Western counterpart during the 11th and 12th century, left the fighting of wars even against infidels and heretics to the imperial government and contended itself with matters of faith and the spiritual struggle for people's souls. According to most Byzantines, wars were not meritorious or holy, and they were not opportunities for noblemen to display marital prowess in the search for glory. According to Dennis, the Byzantines were not a warlike people, and this is reflected in their defensive attitude towards war. Wars were justified in so far as they brought about peace. Dennis writes that this is the main reason why some crusaders viewed the Greeks as cowards.However, this seems to me to be an oversimplification and to some extent an idealizing view of the Byzantines.
Now that I have considered some doctrinal differences it is worth asking: what did the Byzantines think of Catholicism in general? As I have already noted it is impossible to speak of a general opinion – different churchmen had different opinions. Yet I believe some general trends can be distinguished. Before the First Crusade, when contact with Westerners were to a degree limited, the Byzantines adopted a rather condescending attitude towards the Catholics. Churchmen like Peter of Antioch and Leo of Ohrid assumed that the Catholics had strayed from Orthodoxy not out of some evil predisposition but out of sheer ignorance. They also believed that once they had heard what their Eastern brothers had to say they would immediately stop with heresies like the ones I have noted earlier in this text and once more adhere to the correct doctrine. It is important to note, however, that the Byzantines did not maintain that the entire Western church was heretical. Indeed, even the Pope was not seen as a heretic. This is because during the first half of the 11th century the Byzantines did not view the Westerners as a generic group (although this changed later). I will return to this topic in later in this essay.
During and after the First Crusade contact with Westerners and Catholicism increased. This had three consequences. Firstly, it shows that the boundaries between the East and West were not static, impregnable and one-sided. It was not a matter of an active, dominant Western culture forcing its beliefs upon a decadent and passive Byzantine Empire. Instead there was a mutual exchange of ideas and influence. Secondly, it exacerbated the disagreement among Byzantines regarding the definition of Orthodoxy and whether Latins should be considered a part of it or not. This division is reflected in the spread of lists of Latin religious errors. These lists show both that there was an active anti-Latin group and also that there were people who did not view the Latins negatively (why else would you need to disseminate lists showing the Westerners doctrinal errors if everyone agreed about their heretical beliefs?). Thirdly, the contacts with Catholicism and Western clergy gave rise to a need to "downplay" the influence of Westerners upon the Byzantines. This urgency was principally expressed in Byzantine attempts to rebut or disprove Catholic doctrines and “all things Latin”. I think this should probably be seen as a part of the anxiety that some Byzantines felt regarding the Orthodox identity that seems to have been an ongoing issue ever since the conflicts with the Armenians mentioned earlier. This also seems to convey an important change in attitude towards the Catholics. By the time of the first Crusade, it was no longer enough to simply and condescendingly dismiss the Westerners as ignorant – now some of the Byzantines felt a real need to address their doctrines and in a sense to defend their own beliefs. As I have said several times we must not forget that the Byzantines responded to the Westerners in different and subjective ways. There were both friendly and unfriendly interaction between Byzantines and Catholics. Hopefully however, I have succeeded in showing some more general trends regarding Byzantine views on Catholicism.