The problem with these attitudes is that it assumes that only the poor may speak for the poor. What that tends to do is limit the possibilities for reform. The poor are generally under-represented in the media and politics, and often do not have a strong voice in society.
By saying that someone such as Edwards cannot speak of the gap between the wealthy and poor is limiting the voice of the working class. It is essentially no different than saying that a white representative cannot fairly represent a majority black district.
Labels such as "Champagne Socialist" have been around forever, but often some of the greatest strides towards progressive policies have come from those who were not impoverished. Edwards has been given the gift of a great deal of intelligence and a quality education. The fact that he has earned great wealth should not preclude him for speaking on behalf of the poor.
While you may or may not agree with him on everything, he has been derided for being an "ambulance chaser" but has in fact helped many families who would otherwise be unable to afford his services. He should be commended, in my book, for pointing to the difficulties faced by poor Americans. And if you don't think there is "another America" then you weren't paying attention when Katrina hit New Orleans.
Or do you think he should react like Barbara Bush and say " many of the people in the arena here, you know, were underprivileged anyway, so this, this is working very well for them?"
No, your argument is invalid. It might be nice for the impoverished to have no voice, but it is hardly fair to demand it.