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

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

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.

Why do the Republican city officials at Springfield Ohio continue to deny that immigrants are eating pets to sabotage the Trump campaign, even though immigrant pet-eating is now widely believed to be true?

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

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

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

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

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

THE BIBLE IS THE PROBLEM!

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

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?

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

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