If you're of the opinion that Wikipedia should be an insular community, than maybe they should be more honest about it, disable anonymous edits, and save everyone a lot of time. If you think Wikipedia should be accessible, well, it isn't, and that should be fixed, too. Either way, there's room for improvement.
In other words, deletion isn't just about notability - it's also about gauging whether the article will be maintained. Wikipedia's procedures, while sometimes rather obtuse, serve as a first-pass filter to help gauge whether people who are Serious About Wikipedia will actually take care of the article (and of course, even if you are a person with zero edits to your name, reading up on wikipedia's procedures is a good way to prove you might actually care enough about the article to take care of it after it is undeleted).
I will admit that the user messaging feature is _awful_ however. Wiki format is not the right thing to use for a point-to-point conversation.
Mediawiki, and Wikipedia's incarnation of it in particular, is outmoded and obtuse. But it's not hard to do things on Wikipedia. If anything, it's too f'ing easy.
You should read downthread; other people have taken a closer look at Danny Sullivan's real experience working with Wikipedia's processes. This isn't a good case study to make a stand on. Give it a few weeks; Wikipedia will inevitably do something genuinely dumb we can get outraged about. It appears not to have here.
Yeah, this guy was probably wrong, and this particular subject probably isn't notable. Wikipedia still could have given this guy a better experience in the process of figuring this out, and writing this guy off as worthless and not worth listening to is just arrogant and unproductive.
But of course, I don't think this is actually a UX discussion at all; the participants here are:
* An SEO consultant who may have written her own promotional article on Wikipedia
* Her friend, who was upset at the experience he had attempting to convince Wikipedia to keep that article
* Hacker News, which is convinced that Wikipedia suffers from "rampant deletionism" (despite --- for the most part --- never having seriously participated in anything at Wikipedia) and viewing every story about Wikipedia through that lens.