World-wide flood? There has never been a worldwide flood during the brief time that we have been on earth. There are a few potential periods where the earth might have been covered in snow, the last of which might have been around 650 million years ago during the Marinoan period. There have also been plenty of big floods, but nothing remotely resembling what the bible describes.
There is some scientific evidence for a large flood in the Black Sea [1] which may easily have been the basis for a Noah's Ark type story, but not a world-wide flood.
Referring to "Bible fanatics" is no more intolerant than referring to "Tolkien fanatics". If you're being downvoted, it's because you're applying an inappropriate and prejudicial label.
Your point about "Tolkien fanatics" is a good one, but I was not reacting to just one word. As a Toby Mac fan, I like to refer to myself as a Jesus Freak, so mere labels aren't the issue. It's the tone of the whole comment and the inference that one who believes the bible is the literal word of God is an unwise and foolish person.
The only "tone" in "I've never understood why bible fanatics are so fixated on that story, it's one of the bible's most conspicuous flaws." is the one you've projected onto it. On its face, it's an honest statement of lack of understanding. It was neither unnecessarily offensive nor was it unnecessarily derogatory. You only see "tone" because it doesn't support or affirm your worldview.
Additionally, even explicitly saying, "Anyone who believes the bible is the literal word of God is an unwise and foolish person" isn't intolerant. Intolerance is more than just disagreement. Intolerance is saying, "You should not be allowed to think those thoughts," not just "If you think those thoughts, you're unwise and foolish." It's unwise and foolish to think that jumping off a bridge will solve your problems. It's unwise and foolish to believe that vaccines cause autism. Many things in this world are unwise and foolish, and it's meaningless to claim that whenever someone refers to a belief as unwise and foolish he's somehow "intolerant" of those who hold that belief.
It is no more "intolerant" of me to say "If you believe the Bible is the literal word of God you're being unwise and foolish," than it is for me to say, "If you believe that programming languages should be dynamically typed you're being unwise and foolish." The only difference is your sensitivity to those claims.
Your whole answer radiates a tone. Tone is that sentiment that is expressed over and above the words actually used. You could say that tone is found by reading between the lines.
Describing something as a conspicuous flaw is not a statement of lack of understanding. It is an assertion. You can say that you don't understand the Christian perspective on the flood account and then we could have a conversation about it. But making a strong assertion does indeed set a tone.
As a former atheist, I understand the perspective that causes people to make such statements, but please do not confuse my willingness to point out such things with being a sensitive little snowflake. Your whole reply is intolerant because of the combination of your statements and the tone you have used. Methinks you are the sensitive one here. :-)
Mostly just those from the subset of Christianity called "Fundamentalism" [0], which was founded around a hundred years ago as a reaction (IMO, an overreaction) to "Liberal Christianity" [1]. It's worth reading up on the history of those movements to get a clear understanding of where the modern move toward strong literalism originated.
You may also find it worthwhile to read Origen's De Principiis, particularly book IV sections 16-22 [2], and Augustine's On the Literal Interpretation of Genesis, particularly chapter 19 [3]. I've found a number of very early Christian scholars tend to treat certain sections of the Bible (particularly the first sections of Genesis) as not being intended to be understood literally.