Repression: A Social Construction
Foucault, in his typical non-ontological style, does not attempt to debunk the repressive hypothesis by proving it wrong. Instead, he guides us a dimension outside of the question of repression, to show that the entire notion is a social construction. He shows (broadly and very vaguely) how the idea evolved over centuries to become what it is today in discourse. 
Foucault helps us to see repression not an an ontological fact or fiction, but as an idea that that is currently in common use in the West.