Why does it matter so much to atheists that God doesn't exis...

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.

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?

What would happen if the Earth stopped spinning for one minute?

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

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

A belief in a god is not the problem.

What should you answer when someone says to you in French, "au plaisir de vous revoir"?

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

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

THE BIBLE IS THE PROBLEM!

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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 .

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

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