I haven't read that book but have seen so many people mention his #1 plank which is that you will probably die when you reach 200 hours, or whatever it was.
The man should have gone on "Statistics 101". Correlation is no evidence for a causal relationship. There are loads of potential reasons why accidents peak around certain points in the pilot experience. It could be down to the alleged excess confidence or it could be a change in the mission profile. Without analysis one can't say much, and even then the conclusion will still only apply to the population rather than the individual. It's like saying that if you take a certain brand of contraceptive pill you are only 10% likely to get pregnant.
I agree that pilots do bitch rather a lot but let's look at why. Here in Europe there is a great deal of cr*p that any pilot has to deal with on the ground, and there a a lot more cr*p on top of that that any aircraft owner has to deal with on the ground. This, together with the relative lack of utility value in GA etc etc, means that most people chuck it in fast, and that the people who do hang in there tend to be strong determined characters. These people tend to be opinionated (no push-over type will survive in this game for long) and this shows up in pilot forums.
There is nothing wrong with being opinionated! When my children were very small, they used to say "Papa, you know EVERYTHING, don't you?". I used to reply "I don't know everything, but I do have an opinion on everything". 10 years later they get the joke.
The problem with pilot forums is that you get a lot of people who are opinionated but who rarely (if ever) fly. These people have nothing to contribute (except idle chatter) but they still manage to run up 10,000 posts within say 3 years. Everybody else then has to wade through this dross. If this was Usenet, one could killfile them but this can't be done with web based forums - unless somebody writes a custom front end. The Usenet equivalent of Pprune or Flyer forums would have large killfiles and would take just seconds to read - per day. Whereas if you wanted to read the whole of say Flyer you would spend several hours per day in there. Web based forums are a massive step backwards in this respect.