A polite response to someone saying "you don't have to be like that" would be acknowledging their comment while expressing your perspective in a respectful manner. Here's an example of a polite response:
"I appreciate your concern, and I understand where you're coming from. However, I have my reasons for acting this way, and it's essential for me to be true to myself. I hope you can respect my decision and understand that we all have our unique ways of handling situations."
Remember, staying calm and respectful in your response can help maintain a positive and constructive conversation with the other person. It's essential to express yourself assertively while also being considerate of their perspective.