Where can you view that type of material and not get fired from your job?
http://law.justia.com doesn't exactly have photos of the various crimes accompanying the text of various federal and state codes.
My sort of justification for tagging/not tagging something NSFW is, "hey, if someone walks behind you and glances at your computer screen while you're at work, is it immediately going to draw their attention because its obvious at a glance this has no valid business purpose?" A page of dry text (regardless of text's content): probably not. Nude/nearly-nude .gifs of people? Probably. Footage of open wounds or gore? Probably.
Obviously everyone's workplace and computer-use policies are going to be different and people need to know where they work and what's fine and what isn't but I don't understand how my request things virtually no employer is going to be cool with tagged NSFW so people can make an informed decision is so ridiculous.