Hate begins with words. Seems simple enough. Which words?
[dianebederman.com]
Anything that begins the process of dehumanizing or othering your fellow human being. That said, while there is hateful speech there is no hate speech.
Words that provide false expectations; words that compare one's kindred in a negative way; words that are expressed out of envy and jealousy; words that seek to belittle one's reputation but known falsehoods. Racism.