They are corrupt - literally, “they mock.” The word rendered “they are corrupt” never has this signification. It is the very word - מוק mûq - from which our word mock is derived, and means the same thing. The idea is that they deride religion, or mock at all that pertains to God, and to the retributions of the future world.
And speak wickedly concerning oppression ... - literally, “they speak in wickedness; oppression they speak from on high.” That is, they use arrogant language; they speak in a proud manner, as if they were above others; they use harsh and violent language, not regarding the feelings or the rights of others.