I agree with the people who have said upthread that, as a creation of the Chicago Reader, it started out liberal, it has been run by liberal admins, and thus it tended to stay liberal. I don’t think it gets any more complicated than that.
I would also add, and I think I’ve tried to make this point on these boards before, those who intone deeply about “this message board’s mission to fight ignorance,” as though the message board had some grand and weighty moral purpose, are a little full of themselves. “Fighting Ignorance Since 1973” is up there on the masthead because it’s on the masthead of The Straight Dope, the Chicago Reader column, which is a trivia column. It’s meant to be tongue-in-cheek. It started as a feature (and this was more relevant when it began, before you could Google almost anything) where people could write in and have those little “have you ever wondered…” curiosities satisfied. Here’s a sampling of questions that have been answered by the newspaper column, pulled from the archives:
[ul]
[li]Are bananas radioactive?[/li][li]Why aren’t walnuts killing us?[/li][li]What happened to vitamins F, G, H, I, and J?[/li][li]How many G’s does my laundry pull during the spin cycle?[/li][li]Why does the alarm clock snooze button give you nine extra minutes, not ten?[/li][/ul]
While all those are very interesting, they’re pretty much little curious matters of trivia, not representations of some grave, society-wide ignorance that Wise People have some grand moral imperative to correct. Hence the tongue-in-cheek motto, “Fighting Ignorance.”