The board is left-ish by happenstance. The premise is to dispel ignorance, which means challenging established beliefs and examining them to see if they still serve a useful purpose. Conservatives (by definition, I’d guess) seek to maintain established values, thus they face the larger number of challenges.
Of course, hard-core lefties can get locked into their dogmatic views as well. We has a guy named chumpski around who was (or at least claimed to be) a hard-core communist. His views didn’t go unchallenged (the challenges were detailed and lengthy, in fact). I think the classic “left-wing loony gets shot down” thread is this one, in which a person (now gone) started with the assumption that eating meat was evil and asking with claimed innocence why meat-eaters were willing to be so evil. Hilarity ensued.
Bullshit is bullshit and will be challenged here. The conservatives (at the moment) just have more of it.