The overwhelming majority of LW users appear to agree that the post was in fact useful and high quality.

Let's put aside my rejection of that assertion for a second and consider the implications.

The entire basis of and motivation for JGWeissman's post was that people downvoted and criticised the post in question. Why is it that the current positive vote is somehow important and to be deferred to while the earlier negative vote was something to criticize, judge and change? Is the group consensus valuable only if, and to the extent that it happens to match your preferences?