The word liberal definitely does not leap to my mind when I think of Mencken, although he is famously associated with support of Darwinism, among other liberal causes.
But Mencken ~was~ an elitist...as far as it is possible to get from most modern liberals who posture themselves as populists and are filled with enthusiasm for the ordinary working man.
Here are a couple of quotes (there are hundreds) in which Mencken drips with contempt for simple folk and their beliefs.
On William Jennings Bryan:
He was a peasant come home to the barnyard. Imagine a gentleman and you have imagined everything that he was not. What animated him from end to end of his grotesque career was simply ambition the ambition of a common man to get his hand upon the collar of his superiors, or, failing that, to get his thumb into their eyes. He was born with a roaring voice, and it had the trick of inflaming half-wits. His whole career was devoted to raising those half-wits against their betters, that he might shine.
On chiropractic:
Today the backwoods swarm with chiropractors, and in most States they have been able to exert enough pressure on rural politicians to get themselves licensed. Any lout with strong hands and arms is perfectly equipped to become a chiropractor. No education beyond the elements is necessary. The takings are often high, and so the profession has attracted thousands of recruits retired baseball players, work-weary plumbers, truck-drivers, longshoremen, bogus dentists, dubious preachers, cashiered school superintendents. Now and then a quack of some other school say homeopathy plunges into it. Hundreds of promising students come from the intellectual ranks of hospital orderlies.
He much to self-indulgently and self-consciously iconoclastic to be conservative.
William Jenning Bryant was a crackpot (though a fine Secretary of State) who's supporters were a bunch of Deliverance rejects and snake handlers. Its no wonder he got his a-s kicked twiced by a great REPUBLICAN from Ohio.
Mencken was right in condemning both the Socialist Utopian morons of the Left and the Moralistic morons of the Right IMHO.