When listening to a very short extract or rather the start of a longer talk by Zizek on utopia this is what I understood: that he understands discussion of utopia to be by its very nature a discussion of something which does not take account of material conditions, the contradictions, conflicts and struggles, out of which it arises. Therefore, I surmise, that the discussion of utopia is in fact the discussion of elements which in themselves are not corrupt, in themselves itself having no material expression.