Well, pointing the fact they followed the general racist etc feeling might be informational, but the sage part refers to the many issues he wrote about where he was indeed very prescient and competent -- not some total omniscient figure that couldn't go wrong.
>Quite a few of the socialist, social democratic and communist writers of the period had a public record of deep thorough social and political criticism that rivaled menckens sans racism.
Yes, but few were as popular and influential while doing so. This was a major newsperson, most of the others were fringe voices. Plus their anti-racism went hand in hand with the political ideology that they had adopted -- whereas for Mencken it was not so.
I'm not sure but I'd imagine that Menckens racism very much did go hand in hand with his ideology, perhaps not in a causal way but complementary. As another commenter noted he was very much a misanthrope
Edited: Its also I think worth pointing out when someone who is held up a paragon of democracy, like Washington is, held views that were quite anti-democratic. If this persons vision of democracy was limited, should we not note this? Regardless (within reason) of the time? There were people publicly writing at the time of the American revolution that believed in an end to slavery, the right of woman and non-property holders to vote, etc. There was a reason that The Federalist Papers were written, it was assumed that the arguments for the adoption of the constitution and the government it would create were liable to lose out for a variety of reasons. We tend to collapse the range of debate that was happening at that time.