Not everyone thinks this, but I know an extreme right-winger who thinks this. He is also a conspiracy theorist who thinks non-white people are out to get white people so, yeah, odd.
Not every immigrant is illegal or bad. I know a girl who didn’t speak English for 3 years when her family legally immigrated, so of course she’s been told this.
those people are looking for something to hate. This is also why those kind of people are deadend for humanity. If they get rid of all immigrants they will find some other group to hate and after getting rid of those they will find another again until there are only 2 people that want to kill eachother, if you excuse the hyperbole.