On average it cost over ten thousand dollars per year to educate a child in public schools K-12. That is just government direct investment. There are an estimated 800,000 "Dreamers". Many of those Dreamers have graduated from high school and many from community college, universities, and advanced degree programs. The vast majority of those graduates are contributing to society in some way. Their education was an investment that is paying us back. Now Trump, AG Sessions, and Republicans in congress and the state level want to remove all those dreamers. Even at one year education each that is an investment of over $8,000,000,000 (Eight Billion dollars) of your money that the Trumpers just want to throw away.
Even if you hate each and every immigrant regardless of age or any moral compunction; loosing that much money has to sting. And it isn't just those dollars that we are going to loose. We now have to retrain for all the positions that will have to be replaced. So we pay twice for the same thing and loose the billions of dollars that the Dreamers would have contributed to society.