Counteract Violence with Knowledge...educated yourself about the situation at hand and seek out peaceful, collaborative and empowering alternatives. Violence spawns from an attempt to recover what one believes was pilfered. Whether this was money, land, dignity, etc—violence is only a temporary fix to secure these lost assets and rational, intelligent avenues to make the self whole yield the most sustainable results.
Counteract Anger with Understanding...pause, listen and truly hear the angry voice. Anger is frustration and becomes louder because no one will listen. Often anger can be diffused significantly when given a passive audience. You do not have to agree with the position to support the human behind it.
Counteract Hate with Love...hate is toxic. And perhaps my answer is cliché, but in my personal experience...it is the only way. Every individual is human (with good parts and not so good parts) applying this ideology inhibits the reciprocation of this hate. Hating the hate gives it an excuse to hate more, but by loving the hate...the diseased cycle is starved.