Show a little respect

Having the conversation with someone about what it means to respect another person is a very difficult one. I would like to expect that everyone understands what "respect" means. However, during the conversations, I very quickly get asked "I don't like her, why would I be nice?"

I go into "mother hen" mode. I don't expect that everyone will get along. I don't think it is healthy for everyone to be best friends. Some (respectful) conflict is important. When you are in conflict, you are able to learn about yourself, your values and how you process situations. But when you start escalating a situation and attacking another person, you become just plain mean. There is a difference between avoiding a situation and being rude. 

How is it that I can help students to learn how to politely dislike someone?