That's a good question. Yes, that could be the case.

But I prefer to think it as its their way to perceive the world, not sure I would call it bias. It's more like a collective consciousness of the discipline where you see commonalities among them. When they entre the discipline, their thoughts and ideas are also influenced by classic Scoiology theory and their peers (other sociologists). I see it as a process of learning and reflecting. Left and right are merely two aspects of one reality.

Personal bias exist in all discipline and it is just a way of realisation. We can't reduct personal bias from science because it is based on what we think is (was) right about the world now (in the past). So I wouldn't call it bias.