Performative contradiction.

In an article I read recently the author suggested that,
'Foucault is involved in performative contradiction in so far as
he cannot argue for the value of his epistemic position without
having its conclusions undermine the assumptions they require
for their articulation.'
This is not the first time I have met this argument. One neo-marxis
critique I read on Foucault accused him (and Derrida) of a similar
faux pas,
' all relativist philosophers, Foucault is open to
questions about his own grounding. How can Foucault know what
he claims without some general concepts, without a theory?'
What do you think, did Foucault shoot himself in the foot?

Also, I have been thinking a little bit recently about Gramscis notion
of Hegemony and trying to link this with some of Foucaults work (if
anyone is interested in this I came across an interesting article by
Barry Smart in 'Foucault, a Critical Reader'
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