A couple of obvious reactions come out here. Chris has been hard hitting, but crude and demeaning to male candidates I have missed, and never crude and demeaning to liberal women. The second reaction is why the Chris Matthews imitation? Wallace has carried himself for several years at a level of dignity that far exceeds Matthews, but with Bachman he elects to blot his reputation with a disgusting display of bias and prejudice.
I think Wallace's poor choice of words was his attempt to appear hip. The word flake was common among younger people some decades ago and he was just demonstrating how unhip he really is. Bachman expected and deserved to be interviewed as a serious candidate answering serious questions. This was Wallace's "Couric moment".
That said, a candidate is expected to deal with awkward situations such as this without skipping a beat. she should have laughed off the question by saying something like: Obama has lowered the bar so low that I don't think we can compete with him in that department.