On many subjects (a number of them listed in the article that sparked this thread) people hold very different opinions. Since there is almost never any kind of scientific study of failures or incidents or risks involved in differing equipment, gases or practices in scuba diving, those opinions are often either based on an individual's personal experience (for example, my distaste for rock boots) or on their visualization of how something could or would work in a given situation. How attached someone is to his opinions is often largely a matter of personality, and so is how vocal he is with them. We all know people who are "know-it-alls", and can't wait to give you the benefit of their convictions, whether you have any desire to hear them or not. It's not just in diving
For good or ill (and there is nothing anyone can do to change it now) George Irvine was an outspoken proponent of DIR diving in the early days. George was noisy and so far beyond tactless that I don't really have a word for what he was -- reading some of his rants, it is easy to see how he could be roundly disliked, and the entire system he was representing tarred with the same brush. In addition, I would be quite surprised if there weren't adherents who patterned their behavior off his, feeling that their "superior" training and skills entitled them to be dismissive and unpleasant to anyone without them. And the technical diving world tends to be one heavy on testosterone anyway . . .
But if you step beyond GI3, and read some of Jarrod's essays, you find a much more thoughtful and restrained presentation. And the instructor corps of GUE does not (or at least none of the ones I've encountered do) run around bad-mouthing the rest of the diving world. And in at least a couple of my classes, we were specifically warned against developing an elitist attitude. But the stigma remains, especially in the minds of those who have never actually attended a class or even had a quiet discussion over a glass of wine with someone who uses the system.
I remember my first encounter with the idea of "DIR". I had gone on a dive with a woman who showed me spring straps on her fins. I thought they were cool. (This woman was not by any means, at all, a DIR diver. She just had spring straps.) I went to my LDS and mentioned them, and the lead instructor blew up at me, and said, "Yeah, she dives with those DIR jerks. Why anybody thinks a system that developed to explore a single cave system in Florida works for open water diving is beyond me." Which led me to go look up DIR and Florida cave diving and start reading . . . everything I read made sense, and eventually, here I am, using that stupid system on a regular basis to do Puget Sound OW dives (where it works quite nicely, actually). Neither the instructor who was ranting, nor the shop owner, who has repeated the rant over the years, has any particularly good reasons why DIR is so offensive to them -- except that one of the central proponents of it locally for a long time was someone nobody liked for his arrogance and air of superiority. Seeing a theme here? One bad apple poisons the whole barrel.