Grace,
Quite a salient subject indeed, that the ietf makes an attempt to shed/spotlight perspective on..
Drawing from experience, I suppose the foremost key objectives for blocking and filtering would broadly fall under jurisdictional oversight & control and informational security policing. For this very reason, the subject will at best, forever remain contentious and controversial, depending on whose perspective you seek on the matter. In other words, for a very long time to come, it'll almost be impossible to achieve a universal, unanimous consensus on a firewall that serves "everyone' "anywhere" in this globalized networked digital village that cuts across diverse geopolitical, religious,cultural,governance and even family or personal jurisdictions.
One would delve on and on in finer detail on the subject - and the scope is hugely wide, just as the ietf has disclaimed. However, my best take-away from such a rich discourse is, "Moderated Balance". Ideally, the basic minimum threshold should be; how to strive to achieve the most appropriate concurrence where jurisdictional policing(which is necessary), either at country/government level, corporate, or even at home - assuming you set up a family firewall meets/embraces the inherent guaranteed/enshrined universal freedoms of access to information..
But again, who should police/enforce the attainment of this moderation and balance on jurisdictional authorities..? Using which methodologies..? Who knows..
As ietf aptly puts it in their preamble .... "Whether particular forms of filtering are lawful in particular jurisdictions raises complicate legal questions that are outside the scope of this document. For similar reasons, questions about the ethics of particular forms of filtering are also out of scope"
Plenty of regards,
Harry