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 is the concept of pumping water uphill not commonly used as a source of electricity generation, similar to pumped-hydro systems?

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

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

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?

Why do men first look at a woman's chest instead of their face?

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

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

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

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

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

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

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THE BIBLE IS THE PROBLEM!