Okay correction, he did not say "God does not exist."
If you think you can assert that a god exists...and have no burden of proof to bear...you are just not intelligent enough for a discussion like this.
He is instead saying essentially, "You cannot assert God exists without burden of proof. Also, you're an idiot for trying. (Nevermind that I will not accept any proof ever, and will call anything that you would say is proof not real
But this is untrue.
It assumes a one-sided burden of proof. Rather it's something like this.
This poorly drawn line is a spectrum. At the far end is what I call Batshit Crazy Atheism because it not only includes atheism, but a number of other theories or mindsets like climate change, COVID hysteria, irrational loyalty to unreliable political leaders, fangirling about celebrities, etc. To which most of these things are "I'm gonna have to ask you to prove it." On the other extreme is what we call organized religion. It has not just belief in a God (usually), but a full-scale creed. I'd of course be asked to prove Jesus died on a cross and rose from the dead, Mary was a virgin, etc if my stance were anything besides straight up theism right now. So, theism and atheism both have burden of proof, but both are less than an organized religion (which Batshit Crazy Atheism basically is, a rival religion of sorts). Meanwhile, an agnostic can contently keep being agnostic all day long, with no theists bothering them ever.
With me so far? Well, this spectrum really should read like this.
You see, the burden of proof for an atheist is actually negative. This does not mean they doesn't need it, but instead of proving that something does exist, they have to prove that something does not exist. Unfortunately, in order to do such a thing, you have to actually verify that you've actually done any searching.
I can easily tell you my religious journey, and what led me to believe there is a God. It of course would not convince you (see Moving The Goalposts above), but the point is, testimonial evidence is technically allowed in most courts, even though it isn't as hard as physical evidence. This is positive proof. In order to sufficiently prove that God or a bigfoot or a unicorn or any else does not exist, you would have to either prove a conspiracy to create it (for example, a country trying to convince everyone that some disease is real, or that some prophet existed, or that they were oppressed when none of this happened) or show that in a test case nothing of the sort happened (a failed search). For example, "I know that this Muhammad guy wasn't real because I'm Robert Spencer and I wrote a book about numerous things that didn't add up about the timeline and locations of various aspects of Islam" or "unicorns were just invented to sell merch, actually they hunted narwhals for the same thing." In the latter case, you'd wind up with a similar testimonial about how you wandered the entire world, looking at a bunch of different religions, and none of them seemed to have even encountered God, or you prayed and prayed but God never let your 85 year old grandma live forever like you wanted (grow up!) so you knew that God doesn't exist. The problem with negative evidence is that while a theist only needs one or two freak events to happen to present a convincing case for theism (if you don't basically just say that's it's self-explanatory that a Creator would exist in a created world), the negative evidence has to widen their net to make sure they aren't missing something. Perhaps there are bigfoots but they live deep underground. Perhaps unicorns are on planet Kepler-452b. Perhaps God is within our souls (which you kinda sorta probly don't believe in). The point being that while these doubts are fine, they are hardly a big enough area to constitute absolute (dis)proof.
So, I've been watching, but I've never seen anything of the sort. Just alot of trash talk. Where is this failed search of yours? Because if you "knew since you were a child", I'm gonna call bullshit on that.