Teach Kindness Through Your Own Behaviour
If you want to teach your child to be kind and gentle to others, it all starts with you. Your child learns many things just by observing his parents.
Model yourself kindness in real life situations. Be it with friends, relatives, neighbours or even maids, be kind. Give him the message in your dealings with them that one has to be compassionate. Each individual has his respect and cannot be taken for granted. With practice and reinforcement, he will model being kind to others. If you have been visiting NGOs or any local charity to help the needy children there, take your child with you. Let him see you donating books, clothes, etc.
You can get him to donate too. This way you are teaching him empathy and care. He is understanding that little actions make a huge difference in the lives of these children.
Be kind and courteous to your own child. You cannot be sending a contradictory message to him with your own actions.