Maybe what God is is just the representation of what we want to be good in all of us, even if our ideas of what is good get a little kuckoo.
no physical thing can prevent any non-physical thing from existing, but neither can anything, physical, or non-physical, bind any non-physical thing to what anyone thinks they know about it. there are precisely as many gods, as choose themselves to exist. a number which has never been and never will be known, to anything human. it could be zero. it could be one. it could be absolutely any number at all, from zero to infinity. what we can and do know, is that everything that has ever been blamed on any kind of demon or devil, is the work of our own human egos.
I'm don't class myself as a 'Religious' person, it is my ('Pagan') Faith witch I find gives solace and inspiration Can I prove my Goddess and God's existence? ... only in the way Natures shows. The question is always harder to prove than disprove The way I see it = to each their own - and in the words of an old Irish comedian, "May your God go with you"
how can unicorns not exist, or the flying spagetti monster, or the triangular god of all triangles? nothing human, if anything at all, knows what can or can't exist. only that some things (science/nature) do exist, and a great many (possibly infinitely many) other things, might or might not.