This is because of the Theists weakness brother. Let me explain if you dont mind.
For a theist it sounds silly when a non-theist comes and tells him "God doesnt exist". The same way an atheist would find it silly when a theist goes and tells him "god exists". For both of them the default position is their "ism", be it theism or atheism.
The problem with theists is brother that when an atheist makes this claim that God doesn't exist and tells him "if he exists, prove it" the theist reacts and gets into an argument. But you have identified the weakness and commend you for that. The weakness is that the theist more frequently doesn't respond with the "Burden of proof fallacy claim".
If an atheist is claiming that God doesnt exist, its his burden of proof to prove he doesnt. He thinks his position of "No God" is the default position. So it is your responsibility to make him understand that "it is your default, not mine" so make him understand that its his burden of proof. It works both ways. Vise Versa.
Peace.
Here is how I see it. Proof and all these other related words are in a sense not natural like say the word "gravity". Apparently if you remove humans there would be no proof and what not, but gravity would still be there.
So when someone ask for proof, they are in effect themselves using a cognitive belief system and some of those who demand proof believe that it works on all aspects of the everyday world. It doesn't. It is easy to test:
First we need a test of something, which is apparently as the world functions at least for now universal. No human in earth gravity can fly unaided only using their own individual body. Call that test or method proof #1.
Now test if proof #1 applies to all situations. It doesn't because of cognitive, cultural and moral relativism. So when someone asks for proof #1, I only accept it if it is relevant.
It is not relevant for metaphysics, morality, what matters and is useful, and aesthetics. Now some people regardless of religion or not believe that they can use a strong version of proof, that is universal for all humans, when they can't.
That is easy to test, just check if you can believe, behave and act differently.
So I started my personal journey as an adults as an atheist, but I discovered that I couldn't remain non-religious. I believe things about the world for which I have no strong proof and I in effect judge other humans without proof.
That includes all the versions of metaphysics and so on as stated above, so I made the choice to give up on being non-religious. I believe things about the world including metaphysics and the rest for which I don't have proof, evidence, objective reasons, objective rationality and what not as some people believe they do.
In fact there is a subset of non-religious people, who are in effect True Believers like some religious people. They don't understand the limits of human cognition and reasoning and believe they have proof and what not for metaphysics and all the rest. As for this subset they use a variant of empiricism that doesn't hold up. They are absolutists, because they believe in a version of objectivity, that can be falsified simply by being different, but they don't accept that, because they have an absolute and universal methodology of all aspects or some. But what they have in common, is that they all know what the world really is in the strong sense for all or some of these aspects.
So to me, it is not about religion or not. It is about if you accept relativism when it comes to some accepts of the everyday world or you in effect believe that you have the correct objective, rational, true, real, with proof, logic and what not method for all aspects or some aspects of the above: Metaphysics, morality, what matters and is useful, and/or aesthetics.
Are you in the end a subjective relativism or an objective believer in proof and what not?
Regards
Mikkel