"Shame for the humanities"

A man of the left rips into “The Derrida Industry”. Brian Leiter explains why Derrida’s “legacy is one of shame for the humanities”. Well, maybe so, but I can’t quite understand what Leiter means when he writes:

Was it entirely an accident that at the same time that deconstruction became the rage in literary studies (namely, the 1980s), American politics went off the rails with the Great Prevaricator, Ronald Reagan? Is it simply coincidental that the total corruption of public discourse and language – which we may only hope has reached its peak at the present moment – coincided with the collapse of careful reading and the responsible use of language in one of the central humanities disciplines?

The connection between Derrida and Reagan befuddled me. I’d always thought that “corruption of public discourse and language” and the “collapse of careful reading and the responsible use of language” characterised Reagan’s opponents on the left. I must be wrong.