Along the same lines, fielding Biden knowing that he is polling quite low against Trump is making it more likely that Trump wins. There are 49 million registered Democrats. There are almost certainly qualified, principled, charismatic people in that group that would both energize the core and appeal to progressives, independents, and swing voters.
If the Democrats' stubborn pride allows a Trump victory, then we should lay the responsibility at the feet of those who were best positioned to provide a viable candidate who could win.