Anecdotal evidence is not evidence, though. It's basically on the level of hearsay, if not lower.
It shouldn't be discarded as it could hint at actual evidence being available. It could be BS, or it couldn't, we have no idea. It's worth investigating to determine if you can find actual evidence or not. Only then, if you haven't found any actual evidence, can you discard the hearsay/anecdote, or at least throw it in the "maybe check again at some point in the future when we have better technology or can do studies we couldn't do before or whatever" pile. Maybe it will end up being true, maybe not. We have no idea. It's anecdotal, it doesn't help us understand reality any better. But it could lead to it, if we keep at it!
So it shouldn't be necessarily discarded but it should definitely not be accepted. Only accept things that have been verified.
Most of us, including you Warpus, accept anecdotal evidence as being true in many many situations. So I ask, in which situations do we need verification to prove truth and in which do we not?
His assumption is a lot more than that, his assumption is that all that exists is God. That's a lot more specific than what you said, and unfortunately all it is is an assumption - one that can't even be tested.
We have no way of knowing whether his assumption is true or not. It's in the hearsay pile. Actually, I suppose I would put it more in the "thought experiment" pile.
I think that MS assumes that that there is a fundamental unifying essence and that he calls this entity "god". One could call it any number of things. The Vedic tradition call it Paramatma or oversoul or universal self. It resides in a perpetual state of Sat Chit Ananda. How one calls this unifying essence is pretty arbitrary. The attributes one ascribes to it begin the differentiation and often creates starkly different paths.
If one begins with this assumption, if follows quite naturally that all finite existence, including people, are manifestations of Paramatma or god. Snails, cats and people are all in essence, Paramatma, but each has a different consciousness (and physical form) which limits their capabilities.
The assumption of Paramatma cannot be tested or verified. One has to accept it or not. Anecdotal evidence over several thousand years has led some people to accept it as true.
You assume that the only path to knowing what is true is rigorous investigation, observation, and verification of physical things and processes. This necessarily says that unless we can perform those kinds actions or can see a path to performing those actions, something doesn't exist.
That assumption cannot be tested either. It is not dissimilar to a blind child thinking that the world is limited only to the things it can touch, hear, smell and taste. (Are my biases showing?

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Your assumption has led you down a path that narrows what can be true and biases one's thinking away from anything that cannot be observed and measured.
MS's starting point has led him down a path that allows for a more experiential approach (without necessarily discarding science) that embraces levels of consciousness different from what we typically experience.