When an author uses personal statements to make one side of an issue look better than the other side, what type of bias is present?

This type of Media Bias is called Bias by Omission.

Explanation:

Bias by omission - leaving one side out of an article, or a series of articles over a period of time; ignoring facts that tend to disprove liberal or conservative claims, or that support liberal or conservative beliefs; bias by omission can occur either within a story, or over the long term as a particular news outlet reports one set of events, but not another. To find instances of bias by omission, be aware of the conservative and liberal perspectives on current issues. See if both the conservative and liberal perspectives are included in stories on a particular event or policy.