Bias, in my own personal opinion, is a the worst dilemma a journalist can face. The other dilemmas can be resolve if they have enough conviction and will to overcome it. But, bias is different. As much as you try, you cannot control you mind. Even if you try your best, some aspect of your own personal views will no doubt leaked into the article.
Bias is affect the truth in a level different from the rest. IF your article have bias, your audience would not be able to gleam the truth from a subjective viewpoint and they would be unable to make they own decision regarding the matter. You bias would no doubt affect the audience viewpoints. Bias, however, does not distort the truth more then some of the rest, but it is one of the most difficult to control.