Not much of a refutation, just couldn’t locate the pig statue.
On the other hand, it would be impossible to prove the pact was never made.
On the third hand, by way of observation, Haiti’s history is some pretty strong circumstantial proof it happened. Especially when you consider that the Dominican Republic shares the same island.
Haiti: Victim of Clinton's Old Black Magic
The Catholic view of Satan has it that all who chose to do evil are his spiritual allies. The idea though that anyone, let alone an entire country, can be cursed is much disputed.