tptacek, I appreciate your passion, but actually I don't even feel strongly about the deletiionist/completionist issue. I also don't have any pet subjects that I feel are unjustly excluded.
It is about needlessly driving away good contributions in situations where there is no net benefit.
I don't want to generalize too much, but there are people who care more about the letter of the wikipedia process and debate than they do about the net affect on content quality.
Why not let editors build reputation based on customer service to their peers and to occasional contributors? If such a system was designed and motivated well enough, I believe it could be one way to help the situation. I actually journaled a while writing about ideas to discuss, but lost interest because I didn't know anyone who would care.
I think this mischaracterizes WhitneyLand's fear. The worry is not that the individual edits are crucially important, it's that without a welcoming community Wikipedia will eventually run out of editors willing to do keep the site alive. While the content of Wikipedia won't disappear as a result, one fear is that over time the information will become static and eventually outdated. Perhaps this is acceptable, as older encyclopedias can be a snapshot of their time.
A greater worry that some have is that Wikipedia may change from being a relatively unbiased collection of information to cherry-picking and displaying only one side of the facts. I think it's a legitimate fear that some revisions are being refused because they don't match the desired narrative, and that the "rules" are being (selectively) applied as post-hoc justification. While this may not be an overwhelming problem yet, it's possible that a more inclusive community will prevent it from becoming a greater problem in the future.