I don't think it's fair to say they were "explicitly exempted of being impostors" - Intellectual Impostures focuses exclusively on the use of scientific and mat

I don't think it's fair to say they were "explicitly exempted of being impostors" - Intellectual Impostures focuses exclusively on the use of scientific and mathematical terms by philosophers, as it's often clearly evident when an author doesn't know what they mean, and/or is using them in a totally absurd way. It's easier to catch them in the act of perpetrating nonsense. The four you mentioned just don't happen to use mathematical or scientific terms in the same egregiously nonsensical way. That is very far from the only way of writing bad philosophy. For some of the many others, see David Stove's What is wrong with our thoughts? (which, by the way, features Foucault) http://www.maths.unsw.edu.au/~jim/wrongthoughts.html http://www.maths.unsw.edu.au/~jim/wrongthoughts.html