I agree that the Biden response to the gun-toting You-Tuber was revealing–it showed Biden lacks even moderately calibrated snap judgment–and it was revealing in a way that a) wouldn’t have happened with a non-YouTube debate, in which the questioner most likely wouldn’t have gotten past security, let alone the screeners, and b) reflected Biden’s alleged fatal flaw (or one of his several alleged fatal flaws), namely his cringe-making, unhinged spontaneous reactions.
The big news isn’t the diminution in Biden’s already microscopic chances of becoming President, but the collateral damage to other candidates and the Democrats’ brand. It’s hard to win swing states if gun owners hate you. Biden just exacerbated a problem the Democrats have been trying, with some success, to ameliorate.