First, this idea suggests that there is life after death - but with no God. How is that possible? Short answer: it isn't. If we ceased to exist, as the atheists like to believe, we wouldn't know if there was a God or not - we wouldn't exist to find out.
Second, this idea wonders if our God is not the one true God. This idea questions the sovereignty of God and the reality of His existence. I know that He is the only true God. You and I both know the reality of God and the truth of His existence. The only plausible explanation for this idea is if there was a different god (or gods) - but we know that that is impossible, because we know how legit He is.
Hopefully this basic response answered your question. If you want to know more, feel free to Facebook me and we'll set up a time to have a phone call and chat about it!