This is a spiritual error called monism. It's taking non-dualism too far.

> As there are no real difference between this rock and the other rock behind the mountain that I can't see.

There is a real difference between the two; there must be because they're in different places. Monism requires you to deny actually existing differences by saying they're not "real".

> There should be no difference between my thoughts, senses, feelings, emotions etc and that of other people.

This is what in therapyspeak you'd call "not having boundaries". You aren't the same thing as other people; you can tell because the other people don't think that, won't let you borrow their car, etc. It opens them or yourself up to abuse if you think this way.

> There is a real difference between the two; there must be because they're in different places.

That is according to our human perception. For example a single, uniform 4D object could have a projection in 3D that appears as two distinct 3D objects. I am not claiming that a fourth spacial dimension exists, only that we cannot possibly know what exists.