The author is attempting to explain the difference in objectivity standards in newspapers vs. newer media.
Conclusion: "This contrast in journalistic standards is best understood in terms of differing business strategies."
The author needs to explain how the business strategies led to the difference in journalistic standards.
In a competition-free environment, the top priority was to avoid offending readers. This is how the standard of objectivity developed.
But what is the link between objectivity and offending readers? It seems to be that objectivity is not offensive. The author never explicitly says this, which means that it is assumed. Even if it seems obvious, we have to question the link between objectivity and offending readers that is implied by the author. This is common on strengthen w/necessary questions. The stimulus will present a connection as if it is obvious, but we need to confirm it with one of the answer choices.
This is why D is the correct answer. The argument needs it to be true. Let's try the negation test. What if D is not true?
"Newspapers have NOT regarded objective reporting as less likely to offend people than openly partisan reporting."
If this is the case, then the author's explanation falls apart. It eliminates the connection between objectivity and offending readers. How can the inoffensive business strategy of newspapers lead to objectivity, if objectivity is no less offensive than partisan reporting?