The form of argument is invalid1 -- the possibility of mass delusion is not a sufficient reason to deny any anything. The argument is only reasonable when you already have a very strong a priori belief that the masses did not see what they claim to have seen.I suppose my wording should have been a bit clearer. I am just inductively reasoning (myself) that God is another invalid experience, just like hypnogogic imagery. However, my point was not that everyone should follow my lead, and reject the existence of God for that one reason.
My point was that experience alone is not enough to even give credence to the idea that God exists, and that other lines of evidence would be necessary. I reject the existence of God for a lot more reasons than this one.
1: unless, of course, you're in the habit of assuming everything is a figment of the imagination.