People wanted rules for everything.
People wanted organized play run RAW.
People wanted one way to run D&D.
Gary gave it to them, and some people have never forgiven him for it.
Did Gary go back and forth between "Company Man Gary" and "GM Gary"? Sure, he was inconsistent, and it seems at times annoyed with those who wanted everything spelled out as well as those who then nitpicked about individual rulings.
Some of those articles could get a tad snarky. I imagined Gary thinking "You dumb sons o' bitches couldn't make your own campaigns and run them, you wanted a body of rules you follow 100%, never having to make a GM decision, well jackasses
you got it, so shut the fuck up and play the rules as is for fuck's sake!"
Also the fight between Arneson and Gygax probably had a lot to do with it as well, the more different the games were, the less legal standing Arneson had to get cash from AD&D. He did, but not much.
I also wonder if Gary wasn't making "Company Man Gary" a little bit of a persona on purpose. That was always some of the fun of the "Gary Jackson" character from KoDT, parodying "Company Man Gary".
Of course detractors aren't ever interested in anything other than quote mining in their eternal quest to prove AD&D was everything wrong with gaming and everything Gary ever said was wrong.
Arminius is also right in that most of the "unusable rules" reputation is vastly overblown. They are called that by people that never actually tried to use them, they just heard it on the internet. Except for grappling rules maybe.
That is one thing I liked about 2nd Edition.