That question would seem to be answered in the affirmative by the research below. As I have had a great deal published in the academic literature on "ethnocentrism", I feel I should point out an important flaw in the research: It studies something that does not exist!
"Ethnocentrism" is a theory, not a concept. It postulates that people who like their own group look down on other groups. But all the evidence over many years of research shows that not to be true. Liking for your own group does NOT mean that you look down on other groups. Patriots are not necessarily racist and some people are generally benevolent, for instance -- i.e. some people who greatly appreciate their own group greatly appreciate at least some other groups too.
A further problem is that the research below used experimental tasks as its measures of "ethnocentrism". But experimental tasks have a very poor record of generalizing and so are a poor index of stable personality or attitude syndromes. A carefully validated questionnaire would have been a better (though still far from perfect) measure.
So the research is a very poor answer to the question it poses and the last sentence in the abstract below would seem to be totally unfounded. In short, the research is largely vitiated by its psychometric naivety -- a very common problem in experimental psychology.
Nonetheless, from all the things we know about oxytocin, it is probably true that oxytocin facilitates within-group trust, cooperation, and coordination.
Oxytocin promotes human ethnocentrism
By Carsten K. W. De Dreu1 et al.
Human ethnocentrism—the tendency to view one's group as centrally important and superior to other groups—creates intergroup bias that fuels prejudice, xenophobia, and intergroup violence. Grounded in the idea that ethnocentrism also facilitates within-group trust, cooperation, and coordination, we conjecture that ethnocentrism may be modulated by brain oxytocin, a peptide shown to promote cooperation among in-group members. In double-blind, placebo-controlled designs, males self-administered oxytocin or placebo and privately performed computer-guided tasks to gauge different manifestations of ethnocentric in-group favoritism as well as out-group derogation. Experiments 1 and 2 used the Implicit Association Test to assess in-group favoritism and out-group derogation. Experiment 3 used the infrahumanization task to assess the extent to which humans ascribe secondary, uniquely human emotions to their in-group and to an out-group. Experiments 4 and 5 confronted participants with the option to save the life of a larger collective by sacrificing one individual, nominated as in-group or as out-group. Results show that oxytocin creates intergroup bias because oxytocin motivates in-group favoritism and, to a lesser extent, out-group derogation. These findings call into question the view of oxytocin as an indiscriminate “love drug” or “cuddle chemical” and suggest that oxytocin has a role in the emergence of intergroup conflict and violence.