Sorry for the late response, I'm in the US! I'm also not an economist or a radfem, so if my points are not clear, I apologize!
If you think that only whites or men should be in positions of power,or have economic success or that if they are not, they won't have anything to do, it's a zero-sum game. But they do have lots of other options open to them.
There is plenty of room for others to have economic success, it doesn't have to be gathered in one group or one corporation. For instance, monopolies in economic areas actually reduce the available options for everyone and put all capital in once place. However, if there are other companies doing offering similar services/products, there will still be room for profits. Look at the fast food industry, it hasn't hurt McDonalds to have competitors.
Companies with diversity on their boards usually have greater income than similar companies without. ?Research has shown that diverse teams produce better results. In particular, Catalyst research revealed that more diverse boards, on average, are linked with better financial performance. Corporate America has the opportunity to seize the advantage that a more diverse board can yield in this increasingly competitive global economy.? From the Alliance for Board Diversity, May 2011.
So actually, instead of a zero sum game, there's more to be had out there and white corporations are using it!
Feminism(in my mind) doesn't have anything to say about childcare, why can't a woman choose to care for her kids? Why can't she choose to have someone else do that? Why can't she have a career where she makes enough to support her husband while he stays home? (this to me is the feminist issue, she stays home because he can make more, not because she is the "natural" carer)
It's when the economy slides that people get protectionist/racist/mysogynist (as is happening here in the US) because the pot does get smaller for everyone. But that would be happening even without equality. In the US the first jobs to fall to this recession were professional white collar jobs. (which isn't what usually happens) so with those guys still out of work, you can bet there's moaning about anyone else competing with them.