I touched up an old handout on conflict of interest. Given Trump’s attitude toward the profession of journalism (a medium which is far less convenient for him than presenting his unfiltered messages directly to his followers), this is a topic to watch closely.
The point of “the Rosenthal Rule” is not to penalize any one political viewpoint; rather, the cub reporter who wanted to march in a protest has such a strong personal connection to that issue that it made him unsuited to write neutral, fact-based stories on that issue. A conflict of interest is still an ethical problem even if nobody misbehaves and nobody means any harm. —Conflict of Interest: How Journalists Avoid It