Ethnocentrism is a basic sociological concept, and there is nothing mature about ignoring the effects of ethnocentrism on our culture's thinking.
Don't ascribe to malice what can be ascribed to ignorance. There's no way of knowing what Frontier meant by that comment. It's entirely possible Frontier comes from a background where British Isle-originated surnames are the 90% norm and hasn't had any meaningful exposure to the larger world. Ignorant, but not necessarily malicious, and not deserving of hostility.
Which is why I used the term "ethnocentric" rather than "racist." "Racist" has malicious connotations that I doubt Frontier meant, whereas "ethnocentric" does not have the connotation of intentional malice or hatred. Indeed, the theoretical situation you describe fits in perfectly with the definition of "ethnocentric," which encompasses unintentional biases on the parts of an individual.