There's an amusing parallel with the justification Foucault gives for his focus in the first volume of "The History of Sexuality".
He points out that, for a very long time, people speaking/writing about sexuality have tended to make some sort of gesture at the fact that we can't or aren't supposed to talk about these things.
In both these cases, individuals are talking about broader societal trends. It's not a contradiction if they aren't talking about their own specific experience (i.e. "I'm silenced, therefore I can't talk, listen to me talk about how silenced I am"). An 18th-century writer discussing sex may contribute to the counter-argument that by virtue of their writing about sex, it isn't as taboo a subject as they imply. But in and of itself, it isn't proof that such a trend does not exist.
I didn't really try to make an argument, nor even say I agree with Foucault here--just that I see a parallel and it amuses me.
Caveats: 1) I read this over a year ago, 2) found it enough of a slog that my understanding feels pretty fuzzy, and 3) am still undecided/chewing on the main argument
My impression is that Foucault wasn't trying to deny a trend, but to highlight a number of other trends (including the explosion of discourse around sexuality) to open the reader up to challenging or re-framing their received knowledge about sexuality at the time. His focus is very much on all of the power and control dynamics at this nexus. It's a little hard to distill what I mean by that--because it includes actual sex and sexuality, the science/study of it, who is speaking, whose sex is being spoken about, what kind of sex it is, social/class dynamics, etc.
He points out that, for a very long time, people speaking/writing about sexuality have tended to make some sort of gesture at the fact that we can't or aren't supposed to talk about these things.
You can find a gloss of this "repressive hypothesis" at https://en.wikipedia.org/wiki/The_History_of_Sexuality#Volum...