It's not just because of his stance on SKG. That's just a catalyst.
He's curated this image of being some kind of industry guru, through carefully edited shorts, appeal to authority fallacies and thorough moderation of dissenting opinion.
Because this is the first time (I'm aware of) he's taken such a strong contrary position to a popular argument, it's caused people to look closer and pull back the curtain.
What they've discovered is that they've been lied to (by the "hacker" who gained access via social engineering), and that's what pisses people off.
The criticism of his character has been around for a long time, but his message was always louder. Until now.