Bias, I believe, is not always bad. In the case of a persuasive or opinion essay or speech, the use of bias is strongly relied on and is even important to sway the perspective of another person. This, however, are the only ways that I can see bias as a "constitutional" use for support material. In all other speeches, bias can be tricky to avoid and is not as reliable.
Use of facts and statistics that have been gathered from reliable resources are examples of use of unbiased support material.
But, how does one go about finding 'unbiased' support information when considering articles, websites, or books - and can they truly be 'unbiased'? I would argue that there is no article written by an individual or group of people that does not contain a bias. Everyone is subject to the thoughts, opinions, and beliefs that formulate how they consider different perspectives of a given topic. A bias can be found buried deep in information or even plainly on the surface. An example can be taken from our current Supreme Court. Consider that there is a six to three, Republican to Democrat, lean in a supposedly 'unbiased' court. Though they are supposed to be nonpartisan, each individual has a bias to what they support that is reflected in cases that are taken and reviewed.
Though it is certainly hard to find support information that is truly unbiased, it is not the case that all information with a bias is unreliable. Bias is natural to the human brain, as we all formulate different opinions. The use of information that could contain a bias is up to the individual to determine if the use of bias is minimal, stating true information while hinting at a certain stance, or if the bias goes beyond to the point of the information being one-sided.