Are knowing and judging separate faculties?

This question is inspired by a conversation Adirondackwannabe and I had on tinyfaery’s thread.

My favorite prof once said we are all biased, and the key is to be aware that you will inevitably make certain assumptions because of your unique perception and to strive not to judge based on those assumptions. But is there a clear line between knowing something and forming an opinion about it? We are all, at least to some extent, products of our background, and have been implanted with (or in other cases have formed) prejudices based on that background. Are our prejudices all wrapped up in our perceptions, so that seeing a thing and assigning it content automatically also includes forming a judgment about it? If you think knowledge and judgment are separable – do different people allow opinion into their knowledge-process more than others? Do you think it’s wrong to allow opinion to inform fact, or that it’s just inevitable?