What do you mean by biased?

You can probably say that on average, independents are less biased than Democrats in favor of Democrats and against Republicans, and correspondingly less biased than Republicans in favor of Republicans and against Democrats, although this may not apply to some individual independents.

However, I don't view politics as a line. The terms "left" and "right" were based on seating charts in a legislature. The realm of politics and political views is vastly broader than encompassed by relatively narrow range of the American Democratic and Republican parties, and moreover, there are vehement, nasty disputes even within those parties. So in the broader sense, I would say that every individual person has there own idiosyncratic views, which may or may not overlap well with some political party, and the whole notion of being "unbiased" is somewhat questionable.

Let me put it another way: if scientists say the Earth is over 4 billion years old, and creationists say the Earth is less than 10 thousand years old, should we expect the truth to the somewhere in the middle? Should we ask the agnostics?