This is absolutely horrible. I can't believe that the teacher thought that this would be a good idea to make a request of. Now, if you don't want students talking in your class, that's one thing. But to tell a student that they can't speak their native language in your class? Something totally different. Someone not speaking or knowing a specific language is not another person's fault and or problem. Inappropriate. I would have ended the conversation as respectfully as

Like, you can't do this at all. I'm walking away. I'm not entertaining this conversation regardless of what age I am and what situation I am. I'm ending the conversation and I'm walking away. And the consequences and repercussions will be what they'll be and I'll deal with them accordingly. But I'm not entertaining this. And as far as somebody feeling a certain way about not understanding the language that's spoken around them, that's their problem. Learn the language, get better.