I've been thinking a lot about this type of thing and have come up with what I think is a reasonable understanding. Unfortunately it requires some context and I haven't been able to boil it down to a one-liner.
Ignore potential enemies such as Russia and China for a moment. Instead, think about our "best friend," the UK. What are the odds that the UK has hacked our politicians and has dirt on every major politician from the past few decades? I would estimate this at 100% chance. Everyone who can hack does. And they hack their allies as well as their enemies. If we had a chit chat with UK where we agreed to stop hacking each other, what are the odds that we'd go back to our respective corners and stop hacking? That's gotta be 0%. The intelligence community on both sides would never stop. If someone gets caught, publicly, hacking us, we'll shake our finger at them but not really raise a fuss. And we'll do this pretty much no matter who does it. Because it's just standard operating procedure for global politics.
So where does that leave us with China and Russia hacks? What is so particularly upsetting about the Russia hacks as opposed to the Chinese hacks or UK hacks? I think the distinction is disclosure. Hacking information and using it covertly is one thing. Releasing your dirt on the leaders of foreign Democracy-ish countries is tantamount to attempting to overthrow that government. That is what Russia supposedly/apparently did and what makes it different from China. Russia literally attempted a coup. I think there are legitimate arguments to be made that it was ultimately ineffective, maybe Trump would've won anyways, etc. But if the hacking/release allegations are true, then this was nothing short of a coup attempt. Not necessarily in favor of a Russian puppet, but at the very least in favor of a (Putin) preferred government.