I haven’t read the whole thread, but to answer the question, Trump doesn’t dislike Mexicans per se – he objects to illegal immigration. There is the thought that illegals will do jobs for less money than those entitled to work. It follows that those who would normally do those jobs are unskilled and among the lowest paid anyway, so illegal immigrants have a detrimental effect predominately on the unskilled, lower paid, worker and therefore the poor who are entitled to work lose job opportunities – hence they get poorer.