This is not how the burden of proof works. "God exists" is an assertion that requires evidence to prove. That which can be asserted without evidence can be dismissed without evidence. It is not up to us to disprove something that doesn't have evidence to support it in the first place, just like you don't have to disprove that there's an invisible purple dragon living in my garage when I claim there is. The claim never had any merit in the first place, so it should be dismissed.