In most cases, the best way to address an angry, hateful message is with No Response. Hate needs hate to fuel itself and keep itself alive. Like a snake eating its own tail it soon becomes nothing.
“No Response” is different from “No Action.” What would constitute “action” in each case is as varied as there are hate-situations. Attempting to understand what caused the person’s outburst in the first place is one possible, more mature solution.