The original idea of "NSFW" is to not show content that might be problematic for someone at work.
I personally don't have any problem with violence being visible; an employer isn't going to care, and nobody's going to care if I'm viewing a violent video in a restaurant or something. But I'm American. Maybe there are places where there are cultural differences. I would like the option to not show nudity in thumbnails and inline images, but that's not a factor for war videos. As far as I'm concerned, the community not being flagged NSFW is fine.