Ham’s words actually imply (to me at least) that even if God Himself came down and said “you read My book wrong,” he would reply with “This book is right and you are not God.”
That pinpoints the danger in Ham’s stance, and that of others like him. In order to persuade himself that the Bible says only one thing, says it clearly, and offers no other statements to the contrary, one must already have excluded, ignored, or explained away some of what is in the Bible. And so not even the Bible is being allowed to change such a person’s view of the Bible.
Their ultimate authority thus turns out to be themselves, and it is not clear how or whether anyone, even God, could change their mind.