Their mantra is Asia for Asians, Africa for Africans, and Europe for Europeans. When someone says that to you, the obvious retort is: Then you must believe that the Americas and Australia are for Aboriginals! Then you must believe that European Colonialism was very wrong, and upset the “balance” of the continents! (Perhaps the Europeans venturing into the other continents set up the history and politics that result in the current immigration from those countries back into Europe.)
They bring up the history of slavery and note that blacks sold blacks. When someone says that to you, the obvious retort is: You mean the peoples of Africa were divided by nations and tribes and not by skin colour? Just like Russia, Germany, France and England? (Being white doesn’t automatically make you a permanent ally.)
They say that slavery was an acceptable part of culture in Africa. When someone says that to you, the obvious retort is: You must agree then that integrating the children of slaves into the dominant society (as Africans did) was an efficient method to boost their nation’s population of citizens. (America invented the never-ending congenital slavery based on race.)
They say that immigrants drive down wages. When someone says that to you, the obvious retort is: Well we obviously must make all employers legally responsible to pay a wage that an existing citizen would find acceptable, then unemployment would go down among citizens. Employers that wilfully exploit people are contrary to our values of fairness and equality among citizens. (Choosing to treat another class of people worse than our own in our own country starts to sound like economic slavery to me.)
The best argument is the truth. Truth is found in education and in the history books. If your history books present issues with a narrow focus instead of a broad view, you might want to read a variety of history books from a variety of sources. If your arguments are based on emotions and gut feelings, you might want to consider using logic and intellect for a change.
On your mark, get set, READ!