mind boggle. whats a boggle? I dont get it

Here are the words from the killer posted in liveleak:
Total War Against Humanity
Hate, Im so full of it and I love it. That is one thing I really love. Some time ago, I used to believe in humanity and I wanted to live a long and happy life... but then I woke up. I started to think deeper and realized things. But it was not easy to become existential... knowing as much as I know has made me unhappy, frustrated and angry. I just can’t be happy in the society or the reality I live. Due to long process of existential thinking, observing the society I live and some other things happened in my life... I have come to the point where I feel nothing but hate against humanity and human race.
Life is just a meaningless coincidence... result of long process of evolution and many several factors, causes and effects. However, life is also something that an individual wants and determines it to be. And I'm the dictator and god of my own life. And me, I have chosen my way. I am prepared to fight and die for my cause. I, as a natural selector, will eliminate all who I see unfit, disgraces of human race and failures of natural selection.
You might ask yourselves, why did I do this and what do I want. Well, most of you are too arrogant and closed-minded to understand... You will probably say me that I am “insane”, “crazy”, “psychopath”, “criminal” or crap like that. No, the truth is that I am just an animl, a human, an individual, a dissident.
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Wackjob