Meh. You have editorial control, and you know what type of voice you want. You enforce the voice. There's no point in trying to satisfy everyone because you can't. For example, Wikipedia was seen as a den of communist atheist propaganda and so Conservapedia was created.
Sure you could publicize your approved list of sites, but then you're just going to attract a bunch of people with an agenda to trying to promote their agenda by claiming some sort of slight by not being included. In the end though, the only honest response to this criticism is, "Screw you. Make your own site."
Topics aren't blacklisted except when they duplicate something else. Most topics simply aren't approved for trending. If you want to know what's not approved, look at Twitter trends, it's full of junk. Honestly, that's the best public example of what the trending topics algorithm detects.
You really need to read Tom Stocky's post about this, because that's exactly how it's run. But you don't really have to, because it's exactly what I told you.
Finally, if you actually click on any of the trends, pretty much everything on that page is algorithmic. Find a trend that mentions, Obama, I'm sure you're going to find a racist post on that list, because there's always scummy people.
PS. For the record, I always feel dirty if I visit HuffPo. Gawker on the other hand, I'll own up to reading that tabloid.