Ethical relativism is the view that what is ethically right or wrong is determined by the culture. What the culture says is ethically right and what is truly ethically right is one and the same thing and what the culture says is ethically wrong and what is truly ethically wrong are likewise one and the same thing. Let us take the example of child marriages that is prevalent in some Asian countries. To natives from places such as India or Pakistan, child marriage is an accepted cultural belief. The same idea is not true for westerners who find such beliefs against ethical morality. A native from Asia would be accused of ethical wrongdoing if he believes in child marriages, by westerners. A westerner would be accused of trying to impose his own views on the Asian people. There is an obvious ethical relativism here.
One cannot argue the cannot legitimately reason from statements concerning what is the case to statements concerning what ought to be or should be the case, that you cannot infer an ought from an is. As an example, one cannot make a statement that fat people overeat, are lazy, and are ugly and this is a naturalistic fallacy. People are fat because of a number of reasons and overeating may be one of them. While some fat people may be lazy, that is not really so and millions of fat people are hyperactive and rush about doing a number of things. The issue of beautiful and ugly is in the perception of the viewer. To some fat is ugly but to some, fat is indeed beautiful.