Information, as long as it's true (which is in this case seems that it is) isn't political or narrative driven. It simply exists for people to make of it as they will. Regardless of all sides being hit, the dual purpose of deterrence and punishment are met by any leak and is therefore beneficial. All you're saying is that we need more leaks, which I agree with.
All countries influence elections by their very existence. Russia flying planes over Syria caused Hilary to call for a no-fly zone, which certainly influenced the electorates opinion of her one way or another. Mexico provided a narrative that Trump used. There is always influence from foreign states, and it is fair game. Tampering is harmful, but releasing information is not tampering. Furthermore, you can't conclusively prove that it wasn't done to all sides. Maybe China hacked the RNC and found nothing, nobody knows. Your argument rests on a scenario happening that is impossible to prove or disprove.