What's wrong with calling German people Germans?

Culture is not the same as stereotypes, because they tend to be oversimplified, demeaning, and not necessarily accurate. There is not a thing wrong with bonding with someone over shared culture but that's not what the word stereotypes means. Stereotypes are what the Nazi's used to demonize and other Jewish people so they could justify oppressing and murdering them. They are what white people use to justify keeping Blacks out of positions of authority. We can possibly learn more about someone through their culture; we rarely can learn anything about who they actually are through stereotypes.