Why does it matter so much to atheists that God doesn't exist?

Because these are not any gods rules we are talking about.

I am speaking to the US Bible thumpers here, of course ~ many of whom are flat-earthers who deny evolution and see scientists as evil people who are constantly trying, and succeeding, in disproving their beliefs one by one.

A belief in a god is not the problem.

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Those rules that you are trying to reinstate are rules made by men who didn't know anything about the earth, nor anything about all of the other inhabitants of it. How can you not see that?

THE BIBLE IS THE PROBLEM!

The people of the modern world have evolved past all of that nonsense.

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IT does not matter, mainly because it does not exist.

My problem is that people who try to shove their rules down everyone's throats - including by physical force - DO EXIST .

And then use and ENJOY these fantastic scientific advancements every single day of your life?

What was the most challenging shift you experienced as an ER physician? Can you describe the details and reasons behind it?

And how do you deny hundreds of years of advancement in all fields of science?

I do not personally care if you believe in a god or not.

Notice that I said their rules, not any gods rules.

What are some things you would change about Avatar: The Last Airbender if you were to redo the series?

These are man made rules - made thousands of years ago for the use of the humans who lived thousands of years ago.