Hate speech is like porn. It's a case of "I can recognize it when I see it." It's certainly not something objective and it depends on the cultural background of people to define it. The author can't define it because the very definition of hate speech will vary from place to place and person to person.

The author makes other mistakes too such as thinking history that was already written is an absolute truth when it's actually something subjective written by the "winners." I lived through that once, the history that I was taught as truth in my school many years ago was proven to be false a few years ago and the lies were based on what today you'd consider hate speech.

I think the moment we can solve detecting hate speech using a machine will be the same a machine can pass the Turing test because it's impossible to define hate speech in objective terms. Meanwhile we have two equally incomplete solutions: allow all speech or let some people subjectively censor things. Neither of those things will satisfy the author of this post (well maybe the latter will).