I think the ability to make that kind law is fair enough but its implementation is often hysterically overdone. Moonshadow's comparison to the fear of witches might be a good example of what is going wrong with the system.
I think we have progress, then. So, whether the subject is 'child porn' or 'spells' or simply 'thought crime'; in your opinion what has actually gone wrong with the system? Is there some kind of rational distinction between justifiable prevention of harm to children and thought crime based upon same? Or is it all just an arbitrary line that we must all respect, once some government body has negotiated the line?