What has English got to do with how people at a place call themselves or their area? Another example is 'Germany'. What's wrong with calling the place 'Deutsch

What has English got to do with how people at a place call themselves or their area? Another example is 'Germany'. What's wrong with calling the place 'Deutschland' like the German locals do in Germany? Sidenote: /r/AskHistorians is an elitist subreddit that is a good match for StackOverflow as a collection of assholes.