Perhaps the most effective discussion will ask the students to think about who is really being cheated when someone plagiarizes.  Copying papers or even parts of papers short circuits a number of learning experiences and opportunities for the development of skills: actually doing the work of the research paper rather than counterfeiting it gives the student not only knowledge of the subject and insights into the world of information and controversy, but improves research skills, thinking and analyzing, organizing, writing, planning and time management, and even meticulousness (those picky citation styles actually help improve one's attention to detail).  All this is missed when the paper is faked, and it is these missed skills which will be of high value in the working world.  A degree will help students get a first job, but performance--using the skills developed by doing just such assignments as research papers--will be required for promotion.