Good manners dictate not disrespecting others, no matter how justified we think that we are. Manners have their source in violent societies where the powerful must be given signs of respect for their power, or where the consequences can be deadly, even horrific. Shaking hands, with the right hand, began as a way to demonstrate that there were no hidden knives or weapons in the most dominant hand. In some cultures, the right hand is used to wipe after defecating and to use that hand to touch another person is rude beyond belief.
In our dealings with others we must always be motivated by kindness and consideration. In order to be happy ourselves we must not only receive, but also give, and make others happy. Our face is the first and most important object observed by others and its expression conveys to them our emotions and thoughts. A cheerful, kindly, smiling face will go far in attracting people to you. Think kindly of others and your face will show it; you will attain charm and poise of the natural, not superficial kind, because it will come from your heart and people will feel that it is genuine, not made to order.