The banned like every conservative blog site out there. This basically turns the already liberal circle jerk called /r/politics into an echo chamber where no dissenting views are allowed. At least before you could get some discussion before all the left wing downvotes drowned any post critical of the administration.
I can't speak for that because I don't read political blogs and thus don't know their various biases, but I can say that motherjones is one of the most liberal websites on the internet. See also salon. Both are banned. I'll repeat what I said below: Blogs, left or right, don't fit into this. A quick scan of their allowed domains shows that they're mostly newspaper websites, which will potentially have their own biases, but are at least sources of news. It's a news subreddit now. This discussion continues to be unilaterally irrelevant to hubski./r/Politics is a subreddit for current U.S. political news and information only.