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.
See, back then, there used to be this thing called ‘an education’ that every functioning member of society was expected to have. Basic reasoning skills, the ability to reason and all that - it was meant to separate sapient species from animals and solve problems by means of discourse, debate and, worked well for a while. Then this group started shouting really loud, and the other group thought not to engage in uncivilised behaviour, hoping good sense would prevail and restrain what was largely seen as an anomaly. Only the shouting didn’t end. Instead it turned to screaming, then hollering, and started to drown out reason and logic and everything we had developed as a society up til that point. And it worked, so more people started screaming their basal instincts, until the voice of reason was eventually drowned out, then silenced. And here we are today.