Is it right or wrong? I don't know.
Germans don't speak English with a German accent. But they don't speak German with English subtitles, either. They also don't speak American English. There are things Germans say that wouldn't sound right in a standard American accent. Like:
"You are trying to turn me into a cabbage."
I'm not sure what Jon Voight meant by this but it sounded authentically German, the way he said it.
Speaking in normal accents can create other problems. Watching the British production of The Three Musketeers with Michael York and those other English guys, I had to keep reminding myself that they were French since they all spoke in British accents.
There was a British production of One Day in the Life of Ivan Denisovich. It probably made sense to British audiences, but Americans couldn't figure out why working class Russians were speaking with cockney accents.
Roger Corman shot the movie Von Richtofen and Brown with the Germans speaking standard American English. The fellows at United Artists were horrified and had the whole thing dubbed into German accented English.
There were some exploitation film producers in the '30s. They realized that the way to make money was through merchandising. They would show movies about venereal disease and sell books on the subject as people walked out.
They made a religious movie. Somewhere in the South, there was "Passion Play" performed every year. They filmed the play. Began traveling with the movie, showing it to audiences. But it did very badly. They couldn't understand what the problem was.
They showed it to another exploitation film producer and he saw what the problem was. The actors all spoke in thick Southern accents. They redubbed the movie and it made money. They sold religious items in the lobby.
