It just scares the absolute shit out of me that so many usually level-headed people are losing their minds over what comes down to one bad debate performance by an octogenarian with a head cold.
It's completely understandable. The entire rationale for Biden's age not being a problem is that he'll have senior issues occasionally, but as a rule he's ready to deal with problems when they arise. The debate was a problem - a crucially important one - and he biffed it, so the rationale crumbles.
On a hopeful note, this suggests that an effective strategy involves something octogenarians are often thought to have: the ability to wait it out until the shrieking and hand-waving among the chattering class exhausts itself.