That one NSFW tagged video was just a test and can be ignored. Hopefully, most reasonable people will correctly tag with NSFW for any pornographic or other suggestively NSFW videos. For those who don't, the videos can be ratioed through community-driven moderation and help "conceal" them, allowing people to avoid viewing them if they choose. Of course, this system is by no means perfect, but it's a start.

The author can use a content-warning e.g. for NSFW content. Content that is not tagged can be reported by users. The report spec has multiple types:

NIP56 - NIP-56 - Reporting

Read more about the NIP56 on {{appUrl}} - NIP-56 - Reporting

Unfortunately not all clients allow users to specify this type.