Is hate ever justified??

I don't believe that it is ever justified to hate another person. Hate is such a strong emotion that really doesn't carry any positive aspects with it. Feeling hate toward another person, in my opinion, is completely pointless. You carry this powerful emotion of intense aversion with you to a point where you want to act on it or express it, which will really serve you no justice. You can't gain anything from hating someone, you'll only put yourself in the 'hated' position with all of the emotional drawbacks to it. 
There is a big difference between dislike and hate. It's in our nature to dislike things but those dislikes shouldn't elevate to feelings of hatred, because in the end you won't win anything, and you're not doing anything progressive for yourself. When you keep that hatred for a long time, it can spin out of control, and do more harm than you intended to, putting you at an even worse standing point.
Maybe there are a few exceptions where hate IS justified. Such as if someone killed your family, then yes, you would probably hate that person. But still, hating the person isn't going to resurrect your family, you won't gain anything from keeping this emotion in you.  They say that learning to forgive the person you hate is what sets you free and allows you to live your life with a sense of peace by acting as the bigger person.  Overall though, to hate a person also must mean that you care; it's justified when you get over it.