When people are introduced with something completely new to them, they generally don’t adapt to it right away, or sometimes, not at all. In the movie, the aliens were immediately unnaccepted and unwanted. They were not treated as human beings, but worse. Before the humans even got to know them, they already wanted them to leave. They wanted to evict them and change their location to an area that had “better” living conditions. They knew that the conditions were bad, but they didn’t care.
It is much easier to assume than to take time to actually get to know something and to understand it fully. This is why many humans judge things by what they seem to be at first glance. When you think of the word aliens, the word is automatically given a negative connatation. This is why the humans in District 9 immediately decided that the aliens were a threat. They forced them to live in dirty, unsanitary, shacks that were piled on top of each other. Then, later on, Wikus needed the help of christopher. This made him see and experience the whole situation from the aliens’ point of view. He could then see that Christopher had a son that he loved very mich, just like many humans; he saw that they wanted to go home but just couldn’t, and never wanted to harm the humans.