Not really. I don't know a place where Foucault is directly refuted, but I'd have to say that (in my rather unscientific mental survey) most discussions of the subject revolve around gnostic influences and the mind body dualism inherited from neo-Platonism. These ideas both fed and were reinforced by Galenic theory, which defined women as failed men. And there was a definite aversion to sexual contact from the letters of Paul onward, made clearly manifest in the lives of the ascetic desert fathers, neither of which are classified as "medieval". Nor is "guilt" quite the right word to define medieval attitudes towards sexuality. Procreation was, of course, natural, and there is a great deal of material evidence for a rather more blasé medieval attitude towards sex than we would otherwise think. My favorite is still a pilgrim's badge depicting penises carrying the Holy Vagina (i.e. Christ's side wound) in solemn procession.

When reading Foucault, it's kind of important to always remember that he's not a trained historian, nor is he interested in being one. Moreover, his project is much more concerned with modernity than it is with creating an objectively accurate representation of historical reality. He is generally very prone to "reading back" ideas.

I would look at Peter Brown's The Body and Society, Maureen Miller's article"Masculinity, Reform, and Clerical Culture: Narratives of Episcopal Holiness in the Gregorian Reform Era," in Church History (2003), and pretty much anything Carolyn Walker Bynum has ever written.

I've always viewed Foucault (including his famous Chinese Encyclopedia quote that never existed) as not a historian, but a philosopher who theorizes with what's possible on the basis of what we believe now, rather than what the precedents were in the past.

Which is of course, the defense of how some of his historically inaccurate ideas could still be useful.

I'd be interested in which Foucauldean text/ project you have in mind. When it comes to Foucault, context really matters. It's less about a claim of historical fact, than it is about using historical texts to make sense of systems of thoughts.

My guess is that it's less about whether Medieval Christian thinkers intensified apprehensions of easy access to sex. But rather, the nature of Christian texts intensified the expression of sex (in language,) gave centrality to sexuality as a site for construction of knowledge and power, and the construction of sexuality within the context of sacred/ profane dichotomy has consequence to subsequent secular expression of sexuality within the context of transgression and limit.

never did sexuality enjoy a more immediately natural understanding and never did it know a greater "felicity of expression" than in the Christian world of fallen bodies and of sin, The proof is its whole tradition of mysticism and spirituality which was incapable of dividing the continuous forms of desire, of rapture, of penetration, of ecstasy, of that out-pouring which leaves us spent: all of these experiences seemed to lead, without interruption or limit, right to the heart of a divine love of which they were both the outpouring and the source returning upon itself.

(from A Preface to Transgression)

Without knowing which text or project/ period of Foucault's works you're referring to, I can be completely off. But my reading of Fouc is less about claims of Christian guilt and the subsequence "liberation," than an attempt to figure out how sexuality became the site of construction of knowledge / power.