Both terms, GOD and SOUL are plagued with being ambiguous but it would seem to me that the best way of winning any debate is going to the core.
And can we not agree that the idea of humans having a SOUL is the core of religion? All of the big 5 religions are centered around the idea of a "soul" and where it will go after you die.
So if we were to concentrate our efforts on convincing people that humans do not have souls. Perhaps there would be no reason or excuse for them to believe in religion...
Why does anyone believe that humans have souls?
Because their experience of sentience is consistent and contiguous over time giving the illusion of a "being" or soul.
I think the 'soul' concept evolved out of a lot of things. When we dream we are in another world that is just as real as this one. Each child seems to have an innate personality regardless of how they are raised - where does that come from? Life is so magical - there MUST be something more to it than blood and guts. Blah blah blah.
I like to ask if bees have souls - and if so, will there be bees in heaven? If there are bees in heaven, are they doomed to an eternity of mindless collection of pollen or will they gain full sentience? What about bacteria and bears?
I'm guessing you include Buddhism in your "Big 5" of religions. There is no soul in Buddhism. There is no concept of self either. The idea that there is a perpetual continuation of the person that is "I" was taught by the Buddha to be an illusion. I find Buddhism fascinating in the idea that it is a 2,500 year old teaching on the subjectivity of perceptions.