The other effect of Pat Robertson's theological position is that it removes us, and our economic system, from any culpability in the human disaster unfolding in Haiti. The buildings and infrastructure down there are substandard and dangerous at least in part because of our exploitation of that society, and the failure of our economic model to work for the betterment of those people. Haiti was a relatively prosperous country before so-called free trade wiped out a good chunk of their agriculture and drove people into the slums near Port au Prince.
Pat Robertson, as a Republican presidential candidate, was a key supporter of that economic model. So, it's easier to say that the terrible conditions in Haiti are part of a supernatural design, than to cop to any doubt that our capitalist, free-trade system is less than perfect.
The "devil worship" excuse also is a subconscious racist appeal to Robertson's supporters, drawing on the history that a successful slave rebellion (that made Haiti the second democratic country in the Western Hemisphere, to the chagrin of American slaveholders) must have been non-Christian, supported by those dark African devils.