I have an American friend who is of German descent, but his classmates always call him Nazi. He is depressed and even wants to die. I wonder why Americans

Being called Nazi is a legacy of history. His classmates know the Nazis best in Germany, and maybe there is no malice in it. He can change his classmates' views on him through his friendly behavior, thus changing his views on Germany. Nazi did great harm to the world, and this hatred may last for generations, so he should also understand the feelings of his classmates.