Piltdown is considered a fake because by studying it, it was deduced to have been a fabrication. It has nothing to do with it being inconsistent with any theories.
Prior to the discovery that it was a hoax, why was it trumpeted by Charles Dawson, champion of evolution who discovered it, if it was incompatible with evolution?
My question is, on what basis would a creationist argue that Piltdown is a fake?
The most credible guess concerning the motives for Piltdown is that it started as a joke, but was taken seriously by some Brits, because they were jealous of German fossil finds. It just got out of hand, and the jokers were afraid of admitting their guilt.
No one ever admitted it was a fabrication, so on what basis would a creationist argue it is a fake?
Possibly because he was the one responsible and wanted to be famous? But you still leave a question open, what would lead a creationist to suspect that Piltdown Man as a fake?