The issue I have with hard atheists (as a hard agnostic) is that you fundamentally cannot "know" that a deity exists or not.
Not any more than you can "know" that the many worlds hypothesis is either true or false. There simply is not a valid empirical test to derive that knowledge.
At best, the hard atheist makes an inference that he/she believes to be very sound based on indirect information, but that leads ultimately to the "absence of evidence is evidence of absence" logical fallacy. It is quite possible for a deity to exist outside of our testable universe, and simply not give a flying fuck about anything we pitiful humans do in our universe sandbox, and thus it does not interact with our universe at all. Please dont go spouting off about orbiting teapots-- That's loaded, intended to point out that conjecture can lead to absurd conclusions. I prefer allegory here, so more like, we are ants on a sandy hill discussing the existence of fish in the sea. The aicthio ants say that the sea isnt real, so there is no evidence of fish existing, so as a consequence, the fish are also not real. The icthio-agnostic ants say they have no knowledge of either the sea or of said hypothetical fish, and the icthio-theist ants say, with intense force of will, that the sea is not only real, but that the great fish will devour them all.
The ants are hundreds of kilometers from any ocean, lake, or stream. They will never encounter the sea. They will never encounter a fish. The absence of evidence for a sea does not mean that a sea does not exist.
The real takeaway here is not weather or not some hypothetical agency exists, but if the actual question itself is even worth trying to answer. For the ants, they will never encounter the sea, they will never encounter the fish, so even though in this example the existence of the fish is taken as a granted, the ants do not profit in any way by wastefully trying to understand the fish. They are better off just ignoring the question all together. The a-icthiast ants BELIEVE that this is what they are doing, but that is not actually true. They "ignore" the question by rigidly taking a side on the question. The most correct solution is to admit that they dont know a damn thing about hypothetical fish, hypothetical seas they may live in, and assert that since the chances of ever encountering either of those are slim to none, weather or not those hypothetical concepts are real or not are moot. There is no use for the conjecture; it will only ever be conjecture, because the ants dont live next to the sea, and cannot test for the presence of fish.
We humans are ants. we live on a tiny ball of mud, on a distant part of one spiral arm of a pretty unremarkable spiral galaxy, which is one of uncountable billions of other unremarkable galaxies that look just like ours. We will likely never find an "edge" to our universe. We have determined that "god" is like the hypothetical fish to the ants-- We have explored our ant hill, and know that a being of unlimited energy could never manifest in our universe (because they would immediately collapse into the biggest black hole ever. Literally an infinite event horizon.) So, we can conclude that we will likely never encounter god, and as such, any conjecture about the existence of god is just as pointless as the conjectures about fish that the ants are making. The question is not worth trying to answer, and certainly not worth the egoist hubris of asserting an answer without sufficient data. Dont be afraid to say "I dont know, and I dont care."
Unless the atheists out there have some radical tech for disproving the many worlds hypothesis, and systematically eliminating all possible modalities of existence other than our own, they make the mistake that the aicthian ants make-- "There is no such thing as a fish." As humans who eat fish all the time, we know with certainty that fish are indeed real. The ants dont know that, and cannot know that. Rather than accept that they really dont actually KNOW the fish arent real, they blandly assert this conjecture, because it fits their beliefs. (yes, beliefs.)
We are the ants. we do not know and cannot know about a hypothetical god. The existence or non-existence of a god is apparently moot to us. There is no reason to ask the question.
It is not worth the energy needed to answer. we dont really profit from such an answer.