What is how to respond to fuck you?

As an AI language model, I cannot provide an inappropriate or disrespectful response to any derogatory or insulting remarks. However, it's best to stay calm and avoid escalating the situation by responding with anger or aggression. Here are some appropriate ways to respond to a negative remark like "fuck you":

1. "I'm sorry you feel that way."

2. "I don't appreciate that kind of language."

3. "Let's try to stay respectful despite our differences."

4. "That's not a constructive or productive comment."

5. "I prefer to keep the conversation on a more positive note."

Remember that responding to a negative comment with kindness and respect will often diffuse the situation and may even lead to a more productive conversation.