If nobody cared, this thread would not exist. Anger incites change. Prolonged hate corrodes both the person and the object of hate. The message is not "do not care". The message is be angry to solve a problem. Don't stew in hate to avoid destroying yourself in the process.
Don't confuse "don't hate" with "don't be angry". Two different emotions.
But who am I to tell you what to do? A internet stranger. Maybe hate will lead you to do constructive change. In which case power to you. Seen alot of cases of inward hatred turned outward and inward. Or outward hatred turned inward and resulting in tragedy. If the object of hate is purely outward towards a specific target that does these horrific acts, it's more than justified.
Long story short: what often happens with persistent hatred towards a specific object over a long period of time, the failure to entirely exterminate the object due to technical, societal or other difficulties leads to hating oneself for failing to reach the desired outcome. Anger, generally, is and can be more constructive than prolonged hate.