I think it's very difficult for any of us to be objective about any subject, especially something we care deeply about, but my objective observation is that liberals tend to be less aware of and less willing to admit their biases.
We see this often, which I'll get to, but first, let me relate how this phenomenon most recently came to my attention.
In a conversation with a saleswoman for online college courses, I expressed my disappointment that the professor of a religion course I was considering for purchase is an avowed atheist. I said that if I were going to spend time studying the subject, I'd prefer the professor share my Christian worldview.
Don't misunderstand. I think it can be profitable to learn what nonbelieving "scholars" teach about the Bible, but the point I want to discuss here is the woman's response.
She maintained that it is preferable, for this largely secular course on the Bible, to have a professor who can approach the subject from an objective, critical and historical perspective, as if a believing professor would be incapable of that approach. But is that true?
Her error is assuming that nonbelief equates to objectivity. In fact, every human being -- and thus every professor -- has a worldview, and that worldview will inevitably influence his perception of the material. Every professor will have made critical intellectual decisions on a multitude of issues in the material, all of which will be influenced by his worldview.
For example, if you don't believe in miracles, you'd be more inclined to discount those verses of Scripture describing miraculous events, from the Virgin Birth to Jesus' converting water into wine to the bedrock Christian belief: the bodily resurrection of Jesus Christ.
Nonbelievers might be more receptive to "higher criticism" and the "documentary hypothesis" and thus less skeptical of the theory that Moses didn't write the first five books of the Old Testament. They might be quicker to focus on apparent contradictions in Scripture that critical examination often reveals are not contradictions at all.
A believer in the divine inspiration and inerrancy of Scripture will certainly bring his biases into biblical exegesis, but so will a nonbeliever. We cannot escape our biases.
But the woman insisted the secular professor is only interested in presenting the material from a critical and historical perspective. A noble aspiration, I concede, should the professor actually possess it, but nevertheless unattainable. Historians and critical readers have biases, too. They can't help it.