Sometimes a single moment can capture an entire candidacy. In the case of Gary Johnson, he just had that moment. And it is disturbing to watch.
There is really very little we can say about this other than to warn you that it's truly bizarre (and note the reporter reflexively recoiling):
Johnson is not a serious option for young voters, not least of which because of his reckless environmental policies.
This tongue-wagging moment just confirms what we already know.