Of course, in 2011 we Hugo voters didn't know that Resnick and Malzberg would become poster boys for one side of the culture war due to the controversy around their column for the SFWA Bulletin in 2013, which ultimately led to the Bulletin itself being suspended and relaunched. I suspect that some people are reading the vote of 2011 retrospectively through a 2013 lens.
I have been poking around online and as far as I can tell, the only person who reviewed both books in advance of the awards was, er, me: see my LJ entries on Chicks Dig Time Lords: A Celebration of Doctor Who by the Women Who Love It, edited by Lynne M. Thomas and Tara O’Shea, and The Business of Science Fiction: Two Insiders Discuss Writing and Publishing, by Mike Resnick and Barry N. Malzberg. I voted for Chicks Dig Time Lords, which is decently internally structured, sticks close to its theme, and admittedly has one or two duff essays but is generally enlightening stuff if you are a Doctor Who fan - possibly even if you aren't. Its title is of course a bit ironic and some people didn't get the joke. (Some people think that "ironic" is a synonym for "ferrous".)
By contrast, the Resnick/Malzberg book really was nothing more than a bunch of old articles assembled between two sets of covers, with no editing or updating; I enjoyed it none the less, but I felt it fell short of being a proper book. When choosing the Best Related Work for the 2011 Hugos, I preferred (and voters preferred) to go for something that feels like a properly finished concept, and which also relates reasonably closely to the view from 2010. If The Business of Science Fiction had actually been edited to look and feel like a book, I would feel a bit more sympathy - but I suspect that most of those now expressing outrage on its behalf have read neither it nor Chicks Dig Time Lords.
As a matter of fact, the Resnick/Malzberg book actually came third, beaten also by the pinko commie Social Justice Warriors who liked Robert A. Heinlein in Dialogue With His Century, Vol 1, by William H. Patterson Jr. It's odd how I don't see any of the slate campaigners complaining about the overlooking of the officially authorised biography of such a crucial figure in the history of sf; but of course they failed to include the second volume, published last year, on their slate so perhaps they are not really all that fond of Heinlein's legacy. I didn't like the Heinlein biography myself, and felt it was deficient as a biography, but I think it objectively meets the criteria of form for Best Related Work of 2011 better than the Resnick/Malzberg book did; Hugo voters in 2011 probably thought so too.
Incidentally the Best Novel winner that year was Connie Willis' Blackout/All Clear. I was very disappointed by that result; as it turns out, I should have counted my blessings.