Honestly, those kinds of books are usually a load of rubbish, exploiting the barnum effect. There's a reason why 60% of psychology studies could not be reproduced or were found to be flawed (compared to less than 10% with physics). People crave an understanding of who they are and why they are the way they are to the point where they'll believe almost anything.

Nearly everyone has parents which are not ideal. If you were to compare the number of gurochanners who had an abusive childhood with the number of non-gurochanners who had an abusive childhood, the percentage should be more or less the same.

I myself did not have abusive parents. My parents were very supportive. Not perfect, of course, but not bad. And my fetishes started since I was young enough that I was still learning how to read. You know that old "Everybody Poops" kids book? In it, there's a picture of a lion eating meat. Back when I could barely read the words, I used to imagine myself being eaten by the lion as that meat. As I grew up, I changed from masochist to sadist, but the point still applies. This was not something that slowly manifested itself from years of environmental trauma. It was just a fetish that appeared earlier than later.

Now, can abusive parents result in the formation of a sadomasochistic fetish? Perhaps. Some people harbor anger and want to take it out on others, and find catharsis in a fetish. Others feel helpless or worthless and begin to enjoy or crave masochistic activities rather than fear the feeling. Does that mean that most, or even a non-negligible amount of people with such fetishes got them due to childhood trauma? Not at all. Post hoc ergo propter hoc.