In my opinion it is better not to pay any attention on such people. Unfortunately, our world is not perfect. If there were only kind and good people in our world, there would be no wars and crimes in it. So it is natural that there will always be a minority of people who will tell dirt about the community. Some of them will be moved by envy, some by nationalistic prejudices or something else but such people will always exist. I know it is easier to say that really not to pay attention on them but we should try.)