I believe you can find quite a few "mean" people who is just working in the Silicon Valley as happy as ever. The correct rephrasal would be "Mean People Fail More".
It would be naive to think that getting along with people well, while being a remarkable trait, isn't the only thing that leads to success. There are a lot of variables controlling that. It's just common sense that if you are good with people, you are more likely to be successful.
Lastly, I believe a lot of people will be spraying this thread with counterexamples as you did, but the greatest example of PG's argument is the one of the people who gave the world the Silicon Valley [1]. He could have been one of the most cherished person of the past century, he could have all the wealth he wanted, but instead he practically died alone, leaving many people with hatred towards him. Because he was "mean".