His own reasoning behind his claim that gold is not in a bubble rests on the current bull market being longer but less volatile than that of the '70s. He also notes that current investment demand is twice what it was at the peak of the '70s bull market, reflecting gold's newfound status as a legitimate investment alternative.
He has a point, but I'd like to inject one of my own: had there not been price controls on gold, its bull market would have started much sooner. The London Gold Pool has to exert its financial muscle to keep gold at $35 in the late 1960s, suggesting that gold would have gotten rolling in 1967 or '68 [or 1966, for that matter] had the price not been suppressed. To make for a fairer comparison, his chart should have overlaid the present bull market with the 1967-80 period. From a mechanical standpoint, that would compare gold as of now to gold in 1977 or so.
Based upon my own sketchy reading of the chart, his point would have carried anyway. Gold more than doubled in the '73-4 crisis and then halved; the volatility over the last two years has been nothing like that extreme. Also, a mechanical comparison sugggests that the current gold bull has a few years before its run is over - perhaps several.
That's why I've gotten gold pegged as being in a nascent bubble, not a full-blown one. The big inflation driver has yet to make its appearance, but once it does the message will spread much more widely than in the late '70s. Gold is more popular now than then; more of the public will be receptive to the hype that accompanies any bubble.
[Admittedly, my use of the term "bubble" does dovetail well with "third stage of a three-stage bull market." I confess.]