Sounds like a liberal/socialist/fabian society kinda guy. His contempt for humanity is palpable.
Quite the opposite, H.L. Mencken was an old-school conservative (basically libertarian) opponent of FDR and the New Deal. He certainly wouldn't have had any use for Clinton or Obama, being an enemy of both political cronyism and the welfare state. I doubt Mencken would like any contemporary politicians very much either, including Trump, since he disliked demagogues and was wary of mass movements in general, for better or for worse.
His contempt for humanity is palpable.
That much is true. Mencken saw himself as America's version of Friedrich Nietzsche.