Hoax hate crimes accomplish three main things, all of them bad.

First, they cause (usually) minority populations to fear for their lives needlessly. People have every good reason to be scared if, say, it appears that someone is hanging nooses around to intimidate them. If there is no shadowy, violent and racist power making such overt displays, then what special place in hell can be reserved for the person who would make others believe there is one, and to fear for no reason? This result, all on its own, justifies throwing the book at those who fake hate crimes.