Why are we writing off a candidate who’s within the margin of error in the swing states he needs to win?
First of all, because he will not end up being the candidate. But secondly, I did not say he had 0 chance, just that it was "pretty much a certainty" (though that is a slight exaggeration). Biden would have some chance of winning, but the real important point is it is much lower than the chance another candidate would have of winning, and for that reason (as well as legitimate reason to doubt if he can do the job especially next term) is why Biden must drop out.