This is not typical Creationist reasoning. It's actually the Creationists' "Alamo", their last fall-back position. Normally they argue by trying to undermine the evidence (for example by saying that radiometric dating gives inaccurate results) boosting it with archaeological and other evidence that appears to support their position.
But in this case, that option's not open to them. The preponderance of evidence is so overwhelmingly against them that they don't even try to argue. The very best they can come up with is "Either they're wrong or we're wrong". Well, duh! That was the proposition in the first place: which of the beliefs is correct? Because they know they'll be roundly trounced on matters of evidence (giant stone monuments and a detailed verifiable chronology versus a story of a man in a big boat) they simply ignore the evidence and reason that they must be correct because that's what they believe.
eclipse:
here is another possibility.
That the flood was local.
The flood described in the bible was not local. Most likely, the Epic of Gilgamesh on which the Noachian flood story is based had its roots in a catastrophic regional inundation. But that doesn't say much for the veracity of the biblical account.