Well, that would have to be proved out in a mismanaged response. I mean, after all, would not his apparent incompetence have to translate into actual incompetence for that to be an issue? Agency administrators come from all walks of life and backgrounds. But, let's look at your assertions...
Turning away firefighters that were not integrated into the response team, unable to communicate with other responders, and very likely to become a resource drain when they became mired without resources, water, fuel, food, etc...
The only example of this, of which I'm aware, was the result of Governor Blanco denying preposition supplies from being delivered by the Red Cross to the Superdome and Convention Center because -- as I understand it -- they were afraid people would more likely stay in the city instead of evacuating, which is what they wanted.
I'm not aware of this...
FEMA, indeed, the entire federal response en y, has performed as expected and, in many cases, way beyond expectations. Your anectdotal situations aside, the casualty count appears to be much, much lower than first "histrionic" predictions warned. Indeed, most of the lingering problems appear to stem from situations created by decisions made at local and state levels.
Again, the federal government responded as planned and WAS prepared. An enemy attack will be treated much differently by the federal government due to the distinction to be made between natural disasters and enemy attacks.
Natural disasters are a local and State issue first.
And this is about party. The Democrats have stooped to levels never seen in politics on this one.