Lessig's presentation explains us why law and technology combined may collapse our freedom. Digital Right Management (DRM) of music has more recently be another round showing that a small cup of copyright concerning the problem of copy oppose the public and the publishers.
So if we take the time on thinking about it, we can be convinced of the necessity of "free culture". The problem is that I don't have the the same persuasion ability to convince my colleagues. And the reasons are multiple. I don't have enough time and all the arguments to counter the university culture, the management of research (the main occupation of many high school scholars), the protection and the recognition they are looking for.
So we need to convince them by using side arguments, and simplifying the main problems, getting them comfortable and giving recognition opportunity (forthemselves and their institution). License is of course a central point of discussion. An interesting initiative in my institution is the portal "Savoirs Partagés" (Shared knowledge or OpenCourseWare in english) where we can find explanation for different licences available giving simple, effective choice for the lecturer, giving him the opportunity to deliver its own course (with limited effort and appropriate license). More than philosophical reasons, we show them direct advantage of delivering free, open resources. And thereafter, we can begin discussion.
One of my middle term goals is to convince some colleagues of this approach. The following step is to promote real cooperation on collaborative educational resources, but that's definitely a long term objective.