Scepticism for Musk/Tesla has been around for much much longer than the fact-checking site idea.

True, although I'd never seen him attacked as harshly as he has been recently. This time it was a lot more personal.

Yes, but this seems new and improved. Media articles were mostly gushing over him for the longest time, now there seem to be much more negative articles and comments floating around. It seems somewhat engineered.

Ok, so that covers the media. What did he do to piss of hn?

It's his repeated blatant disconnection from reality (a.k.a. technically not lying, but...) in his remarks regarding production levels of the Model 3, regarding Tesla's financial state, and most importantly, regarding the capabilities of "autopilot" and refusal to take responsibility for technical failures in said "autopilot."

I wouldn't say HN is mad at him so much as wanting him to be responsible and own up to reality. He's supposed to be an engineer, and Proper engineers don't engage in "spin." Furthermore, "spin" has to be somewhat believable, whereas Musk has had a recent history of blatant falsehoods. Just like HN calls out anyone else when they're wrong (that is, disconnected from reality), HN is calling out Musk now that he's verbally disconnected from reality. HN has a low BS threshold.

I assume most HN readers are impacted by attitudes in the media. We like to think all of our opinions are our own but it's not always the case.