This sounds like what somebody thinks a mass-killers' manifesto should sound like - a simple rant in short sentences, full of swearing. But folk who feel like this are not the ones who leave manifestos.

Manifestos are left by narcissistic types who want the world to understand and appreciate them, or by delusional ones attempting to provide a justification for what they are about to do. They are usually longish, meandering documents tying anecdotes of personal experience in with conspiracy theories and carefully-curated snippets of history. The effect is either 'look how clever I am to have figured this out' or 'I'm doing this as the only way to fight the evil forces controlling us all'. Sometimes it's a bit of both.

So it strikes me that this particular 'manifesto' may be a fake. But even if it isn't, there is no shred of self-hatred in evidence here, just envy against the better off and more successful.