Not necessary, because we know that newer media is more inclined to use openly partisan reporting. Whether individual journalists are or are not as partisan is a separate issue from whether the reporting is openly partisan.

Not necessary, because the specific kind of partisan reporting that people prefer doesn’t affect the reasoning. The argument is based on what newer media and older newspapers perceive as better for their business strategy; what people actually prefer doesn’t matter, because media/newspapers can still have a perception of what people would prefer.

Not necessary, because the argument concerns what explains the different attitudes toward openly partisan vs. objective reporting. Whether newer media are becoming more or less popular doesn’t affect whether the explanation for the different attitudes relates to business strategy.

Necessary, because if this were not true — if newspapers have NOT regarded objective reporting as less likely to offend than openly partisan reporting (in other words, if they thought objective reporting was as likely or even more likely to offend than openly partisan reporting) — then the fact that older newspapers wanted to avoid offending their readers would not explain why they tended to use objective reporting instead of openly partisan reporting.

Not necessary, because the argument doesn’t concern what is an “essential” journalist standard. The argument concerns what explains why newer media adopt a different attitude toward objectivity. Whether objectivity is an “essential” standard or not doesn’t affect the explanation for why newer media is less objective.