I don't think they cancel each other out. Digg has an extremely conservative bias. Half the stories on the front page are basically "Global Warming Is A Hoax Because Jesus Wouldn't Let That Happen"
I hope they can figure out a way to solve this sort of thing going forward. And I'm curious if their choice of either digg/bury instead of upvote/downvote makes it easier to game. I believe it does, as these folks haven't been able to do the same with reddit. I'm not sure, but I believe a story is gone once it gets a certain number of "buries" whereas on reddit a story with a lot of downvotes can be easily resurrected by upvotes. (though I could be wrong about this?)
Also, there's still a difference between something that happens there and what the Digg Patriots are doing in that they are conspiring to game the system. There's no such equivalent thing going on at Reddit.
Edit: I think we see the natural split of progressive v. libertarian on reddit, and both parties are represented very well. Perhaps there's not a neo-conservative/fox news voice, but I would not be quick to blame that on some sort of conspiracy as much as I would on the difficulty one has reasoning with these sorts of extremists. They are not there to engage in dialog as much as they are there to poison it.
As far as we know.
Perhaps another reason reddit isn't as susceptible is that it allows for user-created subreddits where like-minded folks can form such hives.
Too bad I couldn't have caught it sometime between the swing from Liberal Hivemind to Conservative Cabal, it might have been worth reading.