Most people think it is bad to enter a country illegally. Didn't you see the thread on illegal aliens?

Slurs do depend on the context. In a movie representing history, in books like Huckleberry Finn, Of Mice and Men, racial slurs are about the way people used to be, the way they used to talk. That doesn't excuse the use of that kind of language, then or now--but stating a historical fact aloud is neither morally right nor wrong.

Sometimes among friends racial slurs are used to make each other laugh. Many times people use racial slurs because they have not had the opportunity to learn about other cultures.

It many cases, a person will use racial slurs as a means to degrade and to cause emotional distress not based on any true fact to be "proud of". Calling someone a wetback implies they came here illegally, an assumption solely based on the color of their skin, their primary language, and other such stereotypes, etc. The name is meant as a slur because usually the person saying it has no knowledge of the person's history.