It's easy to say "don't take your anger out on someone. They don't deserve it. Take it out in a healthy way."
But we all get upset, we all lash out, we all get sensitive, and sometimes all we know is how to react viciously towards someone else.
Sometimes you get so upset at everyone around you when the problem lies within yourself. 
Sometimes you can lack control and it's not necessarily your fault, it's the demons inside.