At the inception of the Old Town School of Folk Music, we found that folk music transcended politics, religion or any of the issues. It brought people of various persuasions together in harmony and it still does.
The "Us and Them" problem isn't just folk as we know. It's a terrible mindset that eliminates sharing of information and discussion. I don't think that folk music can be used for persuasion of any kind. People believe what they want regardless of what they sing.
Today, I think the bias factor politically doesn't work at all. That goes for Right or Left. Historically, there have been protest songs of the Left that is a small part of the body of folk music. It's harder to find a Capitalist song that extols the virtues of the stock market unless it's a parody. Any song can be used as a doctrinaire interpretation of its meaning just like the Constitution or the Bible.
Labels are increasingly losing their meaning. Many Democrats today are no longer "liberal". What does it mean to be a Conservative? If you care about the environment and global warming, you are a conservative as conservationist. If you believe that bailing out large banks without regulations is foolhardy, you might be a conservative or liberal.
The labels were more sharply defined in earlier times more than they are today.
I don't know too many of those who admired the Kingston Trio who thought of them as a "liberal" group. Even Walter Progressive Party Candidate, Walter J. O'Brien of the M.T.A. was expunged in favor of a fictitious George so as to not cause controversy.
I'm "beating a dead horse" here. Folk music will always transcend any political, religious or ideological point-of- view.