I have a lot of issues with latter 20th cen continental (particularly french) philosophers, but of all of them Foucault is the last one anyone should have an issue with. While he's guilty of some of the pompous and needlessly intelligible stylistics this crew adopted, he at least has some pretty substantial ideas behind his work. Derrida and Lacan on the other hand....

As far as sociology goes, I think you probably realize claiming an entire field is bunk is dumb. In fact you are committing the very wrong you are apparently complying about (writing off the field of developmental psychology). I haven't heard of. a single beef between these two fields btw, must have been an odd textbook.