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

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

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?

Is it possible for people who claim to be genuine and honest to actually not be? If so, why do they behave this way?

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

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

A belief in a god is not the problem.

Only 1,280 Survived: The Near-Extinction Event That Nearly Wiped Out Humanity 1 Million Years Ago - The Daily Galaxy

THE BIBLE IS THE PROBLEM!

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

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

Joshua Kimmich doesn’t hold back following Germany’s 2-0 loss to France in the Nations League - Bavarian Football Works

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

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

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