As there is only one truth, there can be only one meaning.
Bzzzt! You fail Lit 101. More so, since there are whole chunks of the Bible that are basically poetry and / or parables, which are forms that are practically designed to have multiple layers of meaning.
I agree with a lot of what you say, though. GP is making the silly leap from "With no study of culture, context or historical understandings, I can't think of any interpretation of this 5000-year-old near-eastern manuscript except a claim about the scientific origins of homo sapiens" to "therefore, other interpretations either don't exist / are illegitimate / cannot be discussed rationally based on historical data."
I completely understand why people get impatient / belligerent about young-earth creationists. Or religious people in general when their religion leads them to ignore or deny actual real-world data. But when a religious person is behaving sanely and making the excellent decision to view their chosen holy texts as being about life's purpose rather than a scientific textbook... I don't understand why some people then get belligerent and try to force the issue with "No! Clearly you don't understand your own holy texts, because they are a science textbook! And a very bad one, at that!"...