I had to calm down a friend today because someone had a go at her, criticising her accent and where she lived. It's a curious thing- this need to vent one's loneliness or anger.
First thing that I noticed is that this had nothing to do with my friend. The other person did not know her. Yet, there is something familar with this kind of behaviour. How many times do people put others down? In my experience it happens all the time.
The people responsible for such bullying normally lack the resources to make do on their own and need their own sense of worth confirmed in the 'victim's' misery or pain. What a horrible state of affairs.
Sometimes it is difficult to be alone. Sometimes one does doubt one's own sense of worth, when you have no friends to talk to. Sometimes it is easy to get depressed and feel sorry for yourself. Yet, this does not justify such behaviour.
To ask yourself what you have done to make yourself proud, even if such achievements are invisible to the vast majority of people, should be enough to confirm your sense of self. If it is not, here too is an opportunity to impliment changes in your life. To take the other path- and try and destroy someone else's day, is an implicit admission that you really don't have anything good to offer. Only then, is loneliness and lack of worth actually justified.