Imagine all politicians have at least a bit of dirt in secret, documented in some email, text, or photo, on a computer somewhere. Also suppose each politician has varying degrees of dirt, from minor mistakes, not in bad faith, to full on treason. Then suppose there's an adversary capable of hacking any of the politicians' aforementioned secret media. This adversary can now pick and choose which politician they release damaging evidence of. They don't need to release all of it, implicating the politician with the most severe grievances. Just the one the adversary decides they disfavor. In this case, your argument is saying "let's focus on this small mistake, because that's all the info we have."

I'm not advocating that in the real world, the bigger story is about who's releasing the info, rather than the info itself. However, there are issues when not taking both into account.

This requires your imagined scenario to be true. It also requires that the selective release of information is weighed in the opposite direction to what you are seeing.

In specific terms this is equivalent to saying "Russians showed us proof of Dem corruption" and the response by the media is "well imagine that there's worse GOP corruption that they haven't leaked"

The point is that there are plausible cases where you run into these kinds of issues where it’s not as easy as just saying “let’s evaluate the situation solely on the basis of what the info is.” This ignores the who, when, why, that are extremely relevant in this case, as they were this time 4 years ago.

Is your stated standard ever applied for other negative stories?

There are military generals who have served under multiple administrations. When they decide to go to the media and talk about some negative story about one administration, by your reasoning, it means they're telling a selective truth - unless you choose to believe that they only ever had differences with one administration.

There are whistleblowers from the State Department, DOJ, EPA and all kinds of bureaucracies. Are their stories ever met with this standard - i.e. "you're saying the W. Bush administration did this unethical thing, but you aren't telling us what the Clinton administration did". Was there ever a "I'm sorry Mr Deepthroat you may be right about Nixon but you have not told me what LBJ did, and for all we know, that may be worse"