You mixed up some things. Giving job to those willing to work for less pay is the cornerstone of capitalism. Labor unions are on the other side of the spectrum.
Those who welcome poor immigrants and use them to replace well paid natives are hard core capitalists. A kind of people who built United States into what it is today. Every wave of immigrants went through same ordeal and were brought there by those who wanted more profits. Chinese, Italians, Jews, Mexicans...
It's funny how today there is rise of nationalism in United States. When historically anyone could be American, as long he was willing to learn a little bit of American history, work hard and pay taxes. Current state of affair, pro Trump movement and everything he represents, are based on fear. There is no real need or logic behind that shift. Similar state backed project that were results of population being irationally scared over something never managed to succeed. Doomed to fail, such ideas are.