The great instrument of moral good is the imagination.

Behaving well toward somebody depends on being able to picture what their day is like, which is an act of imagination before it is an act of will. Rules take you only as far as the cases they anticipated; the rest requires you to construct, from very little, what it is to be them. That is why stories change conduct more reliably than arguments do.

It is a skill, which means it can be practised. Read fiction about people unlike you, and in an argument make yourself state the other position as they would state it. Cruelty depends heavily on not picturing the person, and picturing them is something you can choose to do.