I'm fully aware that the DNC is under no legal mandate to operate legitimately or honestly.

And that's rather obviously entirely irrelevant.

In point of fact, if the legal standing of their actions is the only thing that matters, as you imply, then the entire notion that Russia willfully acted to harm them collapses. How could Russia harm them by leaking details of things that are not illegal and therefore (purportedly) entirely acceptable?

If, on the other hand, we stick with the way that things have been presented by the DNC itself - that Russia willfully acted to bring them harm - then rather obviously even they are taking the position that the legal status of their actions is irrelevant.

Go ahead and pick either one - I don't care. Either there was nothing wrong with their actions, in which case they could not be harmed by having the details of their actions leaked, or they were harmed by the the leak of the details of their actions, in which case their actions were self-evidently judged to be wrong, and the legal standing of them is irrelevant.