Well, absolute power corrupts absolutely. Apart from that, I'll give you an example of why no one would benefit from fascism. Take the idea of people marrying based on genetics. That would make married couples' lives horrible, but supporters of eugenics could claim that it would benefit the next generation. But then the next generation would have to do the same thing. If it stopped at any point, "genetically imperfect" marriages would return and we would be back where we started. So each generation would sacrifice itself, supposedly for the happiness of the next, but the people of the next generation could never be happy because they, too, would be forced to donate their lives to the same concept. That applies to every tenet of fascism. People give up rights to gain something, but their expected gains are never realized. Finally, even ignoring sympathy, the most efficient society would be an anarcho-capitalist one, since all government creates economic inefficiency. I am not an anarcho-capitalist, but I point that out to show that fascism is not even the most productive system.

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"I am a Tory Anarchist. I should like every one to go about doing just as he pleased- short of altering any of the things to which I have grown accustomed." (Max Beerbohm)