That would be OK, and I say this as a believing Christian, but by the laws of logic, you CANNOT prove a negative.
So it doesn’t work.
They state there is no G-d. Then they say for me to prove G-d exists. Doesn’t work that way. They have to state why they’re an atheist. They can’t just come out with a statement and I have to accept it. Why would that be proving a negative? “I don’t believe there is a G-d because ...” and state your reasons. I don’t believe in global warming. There are people who do believe in global warming. Argument for both sides. No different.