I haven't seen any 'goldbug' claims on here saying you can't invest in a market index.
That's right the timing of their invention and subsequent widespread take up has only occurred much more recently so it's obviously not a 'perfectly valid comparison' when someone puts up a chart showing comparative index returns for very long term periods, say the last 50 or 100 years or so which I've seen proffered by one particular poster on many occasions.
Already expressed and the point of my original post.