Being busy I wasn't able to comment on this den Beste article. He receives a lot of critical e-mails over minute details of his post that don't affect his main point. This annoys the crap out of him; I think he misunderstands the meaning of their criticism (or at least some of it).
Some of us (i.e. me) have no difficulty distinguishing the forest from the trees, but become distracted when we see errors. I had one teacher in undergrad, for example, who had atrocius grammar and spelling. It was irritating to get handouts with obvious errors, and made it difficult for me to concentrate on the material. Den Beste is obviously nowhere near this bad, and blog posts should be held to a lower standard than most writing. But to some of us, when we see what we perceive as an error it jumps out of the page and slaps us in the face. It's sort of like looking at a forest and seeing one of the trees on fire. You want to put it out before it burns down the whole forest.
Well, I think that metaphor has been beaten to death now. But to some subset of people, when they see errors they almost cannot help but try to correct them. This does not mean that they don't understand the point; it's almost like an Obsessive-Compulsive Disorder type thing. But I can only speak for myself and I've only sent Mr. den Beste one e-mail (and made one blog post). While some people may feel this way, it's a good bet that at least as many people are just jackasses trying to show him up and boost their egos.