Stanley Fish on (among other things) the distinctions between fairness and accuracy.
What Pitts is urging (implicitly) is not the condemnation of Ku Klux Klan founders, but the principle that condemnation or the withdrawal from condemnation must be evenhanded. You get the right to say something critical of what someone of the opposite party said or did only if you would be similarly critical when members of your own party said or did something similar. And you get the right to refrain from criticizing some only if you will also refrain from criticizing others.
This is a familiar move in political argument (it is related to the tu quoque, or “so’s your old man” move). We saw it in spades a while ago when Democrats lamented the incivility of public discourse and blamed right-wingers for proclaiming over and over that President Obama was a foreign Islamic usurper working to undermine American values. The right replied by rehearsing the litany of things said by democrats about George Bush — he was a tool of corporate interests, a warmonger and an enemy of civil liberties. So what gives you the high moral ground, those on the right asked, when you were equally vile in your accusations?
I want to say that this is a bad move (and a cheap trick) because it deflects attention from the substantive claims being made and puts the spotlight instead on propositional consistency. The better move (by either party) would have been to insist that Obama or Bush was in fact those things and to back up the assertion with the marshaling of evidence. The better move, in short, would have been to take a stand on truth rather than shifting the focus to a calculation of reciprocal fairness.