As usual, Amanda at Pandagon nails it better than just about anyone else:
I think the purpose of slandering 9/11 widows is that Coulter needs an outrageous distraction to smuggle in the idea that politics is a game and anyone who takes is seriously should be ejected from game play. This is another one of those situations where she has some amount of social support for her assertion, but she’s trying to reinforce it so that others can pick up her ball and run with it. There’s already a tendency in our culture to value detached observation above experience and Coulter’s building on that to argue that anyone who is actually hurt by a government policy or action should be disqualified from speaking out against it….
[T]he ideal response to her whining that it’s not “fair” that 9/11 widows have moral authority is this, “Are you saying that anyone who has a stake in a debate shouldn’t have a voice? Doesn’t that mean you shouldn’t be allowed to speak in favor of the Bush administration, since your wealth means that they’re cutting your taxes?” Or the question about her disparaging evolution should be, “Why do you think arguments without evidence should be prioritized over arguments with it?” Get after her assumptions, folks. The best part is that when you do, she completely loses her cool and it makes for better TV. [Emphasis in the original]