I don't think your logic holds. The fact that it's "an encyclopedia that anyone can edit" is why deletionism is a healthy force. If the deletionists let up, and WP spiraled out of control with vanity articles, it would likely stop being an encyclopedia anyone can edit.
Again, I think people personalize this. The good deletionists don't care about you or your subject. It's the project they're sticking up for, not the non-notability of Trevor Blackwell. When the topic of debate is Trevor Blackwell, they'll lose. When it's Ketchup_salt, they'll win.
There certainly are bad deletionists. A lot of them. But I don't think that's a symptom of deletionism. I think it's a symptom of editing-as-sport and status-seeking, and that those are the problems that are really poisoning WP.
Deletionism nudges the project power more towards those with "editing-as-sport and status-seeking" motivations. Procedural games are what they like.
For new and casual contributors, deletionism forces them to engage on topics they aren't passionate about -- older topics and wikipedia lawyering -- rather than the marginal topics they're excited to get started (and which may become rigorously 'notable' in due time). Some of these people will just be driven away.
'Orthogonal' is the strong claim I'm disputing; other WP process does not create the same problem. For example, editing someone's contribution to improve its voice/NPOV or suggest verification can encourage casual contributors; it's positive attention. "I got something started, others are paying attention, progress is occurring. Fun!"
Deletionism -- whether the judgment that something should be deleted or following through with deletion -- is negative attention. It uniquely discourages contributors and often destroys content of small-but-positive value. (For example, it destroys the important 'first drafts' of topics that will someday easily pass 'notability'.)
Deletionism also shrinks the territory on which collaboration can occur. A deleted article can be neither corrected nor improved; it is a void. Perhaps there is someone somewhere who could add the citations... justify the importance... benefit from the partial information -- but deletion forecloses that possibility, even though cheap storage and cheap search means incomplete scraps of information can better find their audience/editors than ever before.
Again, I think people personalize this. The good deletionists don't care about you or your subject. It's the project they're sticking up for, not the non-notability of Trevor Blackwell. When the topic of debate is Trevor Blackwell, they'll lose. When it's Ketchup_salt, they'll win.
There certainly are bad deletionists. A lot of them. But I don't think that's a symptom of deletionism. I think it's a symptom of editing-as-sport and status-seeking, and that those are the problems that are really poisoning WP.