Well my only full reading of either was Madness and Civilization, which by all accounts I can find was pretty parallel to JPs tenuous treating of mythology, at best.
Madness and Civilization is a study of the history of madness as an idea (a truncation of
History of Madness). It's neither a defense nor a promotion of mythical imagery or whatever; it's simply a work that traces how society's notion of insanity changed over time.
Peterson's writing isn't a critical assessment of mythical imagery in society. It takes that imagery as a means to interpret some golden rule of social organization. It's basically like using the Bible to critique social behavior without asking oneself why/how/when the Bible was written in the first place.
Then we have on top of this the interchange with Searle about the needing to write 10% bullshit or whatever:
http://www.critical-theory.com/foucault-obscurantism-they-it/
And on this, Searle was much more charitable to Foucault than Derrida! So if we want to discuss areas of competency in philosophy, or simply in writing, there's certainly challenges to competency in either for those 2. Now, obviously we could introduce competency in obscurantism, but how can one begin to establish the guidelines for competency, and what is the gain even if one could?
I find it funny that people who dislike critical theory take Foucault's comment as a serious censure of French academic writing around 1970. Never do we consider that Foucault was doing what Foucault did so often in other interviews and conversations: joking. I can just imagine a scenario in which Searle laments the odd style of French theory, and Foucault sarcastically saying "Well, you know, if you're not ten percent incomprehensible, you won't get published!" And knowing Searle, that cranky bastard would jump at any chance to slander continental theory.
But ultimately, whatever Foucault meant is beside the point. Writing falls in the purview of all who consider themselves publishing academics. No one faults Wittgenstein for his often idiosyncratic and aphoristic style in the
Philosophical Investigations. Furthermore, competent and clear grammar isn't absolute or fixed; it evolves according to those reading. Different disciplines promote different kinds of rhetoric. When I read Derrida, I often find it clearer and more cogent than the proclaimed mathematical writing of positivist philosophers. Foucault and Derrida actually didn't like each other very much and had heated arguments. Foucault's interest in history and the treatment of bodies (biopower) aligns nicely with the concerns of Chomsky and Searle, and his later work in particular was quite liberalist in appearance. By contrast, Derrida was interested in language and meaning (not linguistics per se), and how writing itself often betrays the order it seeks to establish.
Critics of Derrida so often make the claim that all he wanted to do was dismantle the system or some such--break down social hierarchies, disrupt language, blah blah blah. This makes Derrida out to be some clandestine political activist, which is quite far from the truth. Derrida was fascinated by the discontinuities that
already exist in language, not with advocating for discontinuity. He was fascinated in how, for example, the Greek word pharmakon meant both medicinal drug and poison/toxin, and how this took shape in Plato's writing. His essay "Plato's Pharmacy" is one of the most fascinating treatments of Greek philosophy that I've ever read, and it's not political at all! It's simply a study of language (and of Plato's suspicion toward writing).
