I think that one of the critical differences between each of the philosophies is their particular aim. Moral universalism, or absolutism, seeks to appropriate the world in accordance to the idea that there are moral certainties that can be articulated. This sense of totality is how an individual perceives consciousness. In the ethnocentric approach, the individual defines consciousness as one predicated upon the belief that one's own ethnic group is at the top of an imagined hierarchy. As opposed to universalism, which places power in the absolutes being articulated, ethnocentrism stresses that power and authority is derived from one's own ethnic group. In each, there is a certain position of power from which one speaks. In ethical relativism, there is an assertion that judgments cannot be made because relativity is what defined consciousness. In this light, judgments and all assertions are subject to social and cultural conventions.
Moral absolutism is a meta-ethical and universal agreement that acknowledges two essential behaviors: right and wrong. It is through moral absolutism that the idea of things being inherently "good" or inherently "bad" comes to life. The essential tenet of moral absolutism is that there is a "moral" as in virtuous, righteous, "backbone" that we all should comply with, or otherwise we would be doing "the wrong thing". Religion is one of the conduits of moral absolutism; its primary task is to guide "flocks" of followers toward a path of ethical, proper behavior.
The ethnocentric approach is not an abstract assumption like moral absolutism, but a measure of comparison used to base decisions, in various fields, that depend entirely on the cultural, ethnic, or racial background of the groups or individuals who are pivotal for a course of action. For example, language and religion are variables to be considered for decision making. The down side of this is that these variables automatically render a decision biased. Moreover, if the variables are going to be used to render one group superior to another, it will be an unethical decision. It is clear that there must be a clear purpose to make any decision based on this approach.
Ethical relativism is a theoretical construct that attempts to explain how morals are viewed from culture to culture: what is good for one group, what is considered right and ethical to a group, may not be defined the same way by another cultural group. The best example of this is the current reaction from the Western world against the practices committed in some Asian countries with dogs, which are slaughtered in mass and then used as food. To that group this macabre act is no big deal. To the American public, this would be considered animal abuse and inhumane treatment of living beings.