There was a time when being a nobleman meant feeling like a different kind of being than serfs or urban artisans. Only other nobles fell into the category of “being of the same species”. Today, we may nurture romantic notions that a shared Christian faith changed relationships, but in fact we have no evidence that it did – unless we are thinking of saints, philosophers or other exceptional figures.
It was only the Enlightenment and nationalism that brought the awareness that the basic community is a nation and not a social class, and that members of the same nation belong together. In this sense, class conflict is not a matter of Marxism (or the bourgeoisie), but a matter of the Middle Ages.
It also implies that it is very difficult for a nobleman to be a patriot. Occasionally someone succeeds, but they are rare cases. For example, the founder of the independent Czechoslovak state in 1918, Tomas G. Masaryk was well aware of this. He banned the use of noble titles and had the largest land seized. We can have a republican system or we can have nobility, but we cannot have both at the same time.