More people than just the right believe things to be a zero-sum game, else you would not see the kinds of things expressed in the Github diversity slide-show you saw in this article [1]. This is the main slide [2]. And, one could argue it is, for every man hired, that's potentially one fewer woman hired and for every one white woman hired that's one fewer minority woman or man hired, if you look at things from an individual company PoV. If you look at it in a broad economic sense, it may not be zero sum, however.
The bullet points hint at the issue being interpreted as a zero sum game. Imagine this slide show from a different ethnic group or gender and how it might be interpreted.
[1]http://www.businessinsider.com/github-the-full-inside-story-...