If you believe PP is in an eliteist clique, you're quite mistaken and am still struggling to see the connection. Yes, I grant there were some ridiculous things in said post which made my jaw drop, but as BribieG points out, probably a bad hair day and it was subsequently acknowledged, as Nick did too, so perhaps its a little disingenuous.
I don't doubt elitist 3Vers exist though, maybe not so much around here at all but
on other boards they exist, and in influential positions (the bigoted JBK **** was a moderator FFS). That also brings up the next point- I hate to break it to some folks, AHB isn't the world's only home brewing forum! A mighty good one it is, just not the only one. Likewise, it needs remembering that guidance for novice AGers does take place outside of forums too, it happens quite a bit in fact.
Righto, to answer the OP. The bewildering terminology and degree of technical proficiency which seemed to be necessary to even try AG. As M^B and others point out, really it isn't that challenging, but as a novice if you scout around a bit, things like water chemistry, perfecting grain crush, stepped mashes, decoction, recipe formulation, lautering techniques and so on make you wonder if you'll ever be able to even make a partial, let alone ever try an experimental AG. It is largely just fluff though, AG is really quite forgiving and it is surprising how hard it is to stuff one up that bad that it isn't even drinkable. The guides, tutorials and so on which demonstrate that AG is doable by mere mortals in their own home without getting a second mortgage are invaluable in blowing away all that fluff.
I quite agree that while its a terrific resource, Palmer is getting dated, just the same way Line for example and despite his foresight, is now dated and so on. But, seeing as it is electronic, perhaps it could be updated to reflect new developments in home brewing, that would be rather helpful.