I don't think bias is always a bad thing. Bias can be defined as opinions or information that clearly agree with one side of the argument. While it should definitely be avoided for the most part, it's sometimes impossible to not have a little bit of bias. I think that it is important to use support that validates your claim...because that makes the argument or opinion stronger. On the other hand, too much bias will cause the listeners to not take the speaker seriously. It is important to present the counterarguments and also validate the beliefs held by people on the other side of the argument. By doing this, the listener will have a greater respect for the speaker.
I love how you talked about the good and bad side of bias. I completely agree!