In the late 20s, the word 'untermensch' started to gain prominence in Germany through its use in Der Stürmer (Nazi paper dripping in racism).
It became more and more common, and it was eventually used in official channels. Its literal translation is 'sub-human', and it was used to describe many.
When you start to dehumanise people, it becomes much easier for the general population to show a lack of apathy, and when that happens it's a slippery slope.
I'm sure if you looked closely enough into the channels used by hard-line Republicans etc, you'd get nuances of Mexicans and whatnot fitting that description.
