"Is this really something you want to dispute?"
Absolutely. They are also the same people who would have first established written language, legal codes, and structures like the pyramids which we still can't figure out how they constructed. These people laid down all the ground work that you take for granted, today.
"and it probably did seem to them,"
This is all supposition on your part. The idea that humans were 'primitive' is derivative from your evolutionary outlook on religion.
"Sntjohnny, you keep trying to make Ragnar's and my point sound ridiculous,"
Actually I didn't read your posts. Sorry.

It wasn't my point at all to make Ragnar's arguments sound ridiculous. If anything, the point was to show that his point was insulting to the human race.
"but even you must realize that the Sumerians lacked our sophisticated systems of education and communication networks."
I personally have no desire to limit the scope of this discussion to the Sumerians. I do not believe that if you don't have a public school system or the internet that you are primitive.
"but the more mundane story that a catastrophic flood triggered a myth is more plausible."
Again, I was responding to Ragnar, not you. I didn't even read yours. I don't even know why I'm bother to read it this time. He responded to the multiplicity of flood myths. So, the problem to be reckoned with in that context is that you need more than just one catastrophic flood, but hundreds, if not thousands.
"1. Your attack on the idea that Sumerians and their ancestors had a primitive culture and knowledge of the world is too absurd to need refutation."
Hopefully you see now that I could care less about the Sumerians or anything that you've said to this point. The idea that they are 'primitive' contains an assessment not of their technology, but their mental capacities. It is one thing to mistake a thunderclap for a god bowling. It is quite another to see a puddle and believe the whole world has flooded. This isn't 'primitive.' This is stark raving stupidity, and it is this which we are required to believe under his hypothesis.
"No, because the primitive nature of that society had to do with ignorance and not inherent intellectual ability."
Aha! This is a game of deception, then. Because of course if a person can't distinguish between a localized flood and a global flood, it is precisely the 'inherent intellectual ability' that is being attacked. Ignorance of what? The concept of volume and quantity?

They see one rabbit and because of their ignorance they think the world is covered with them, 40 deep?

"There is evidence of a catastrophic flood in Sumerian times, but we also know of the catastrophe in the Black Sea area during a time when humans occupied that area."
Again, in context, it isn't the 'evidence of a flood' we're interested in, but rather geologic conditions that could generate 'catastrophic floods' all around the world during the narrow time frame in which all of the flood myths emerged.
Shortly after this, the human ability to distinguish between 'a lot of water' and 'water covering the entire earth' emerged. One might say that this is proof of the evolutionary outlook after all. All the idiots died in the flood, leaving only those with the meme that helped them understand that they needed to get onto high ground, pronto: this was no mere puddle!
"There is no geologic evidence of a global flood historically. If they were. your argument would have a lot more credibility."
As EB said, the geologic evidence is of sedimentary rock all over the place. How is sedimentary rock formed? Through water action. It covers the earth and therefore is evidence of global water action. The only difference in our views here would be that you require there to be trillions of small floods to account for the sedimentary deposits while I posit just one. Here it is a question of interpretation of the evidence, not evidence itself.
"Again, you confuse ignorance and intelligent."
No, I really don't. The only way that people could confuse a local flood for a global flood is if they were all village idiots. And the people they relate the story to who propagate the story are dumber than dumb. This is a requirement of the argument. If we grant your main argument, that people were primitive because they ascribed natural phenomena to the gods, a cursory examination of people who believed that through the centuries will reveal people who can tell the difference between a little of something and a lot of something. But 3,500 years ago, for some reason, all around the world, this capacity was lacking. That isn't 'ignorance.' That is stupidity.
"There are certainly people in this world who believe some pretty stupid things, but that doesn't mean that they themselves are genetically deficient."
Find me even one that would confuse a localized flood with a global flood. Then find me the one that would listen to someone telling the tale of a global flood, and despite being on the globe that is the subject of the tale but not experiencing the flood, believes the tale anyway.
What with Katrina and the tsunami I reckon you should be able to find me some living examples of such 'primitive' thinking.
"True, but irrelevant."
How is it irrelevant? These 'primitive' people would know to get to high ground, don't you think? hmmmmmm? And if they are on high ground, do you think they'd understand that one can't say the whole world is under water? Find me a tribe in Africa who confuses the flooding of their river as a global event and I recant the whole argument.
"I think that the Cargo Cult religions prove that primitive people do confuse their local world with global conditions. It is a pretty natural thing to do."
This is your example? We have a very specific claim here- not a confusing of the 'local world' with 'global conditions' We have an incapacity to recognize amounts of water. Moreover, we have hundreds of stories to account for, not just one or two. One might imagine that an island community unaware of continents might imagine that his island is the world, but what about those on the continents?