Whatever you give, is what you "will" get. Such is this world. Be kind, and the universe will be kind to you. Be mean and the universe will treat you accordingly. Respect and you will be respected in return. Disrespect, and you will be disrespected.
Maybe not that instant, not that day, not that month, not that year, but trust me, karma is a bitch and she will come and get you. You will not find any place to hide. Not just you, but your future generations too. Harass one person, and Karma will make sure your future generations are harassed the same way for the times to come. Whatever you do, you initiate a chain reaction.
Whatever you give (good or bad), you give it to yourself in the future.