Well the main reddits have a sharp liberal bias. When people from other subreddits who don't conform to this view speak up they tend to get smacked down pretty hard and quick.
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.