How to filter Items in Recommender Systems?
Is there a reason you cannot filter NSFW articles as a post-processing step? For instance, if you need to recommend 10 articles, you find the top 50 recommendations and then apply the filter if it is needed and truncate down to top 10?
In my experience, it is pretty common to apply business rules before/after recommendations to account for things like this. Grabbing an example article on this topic for reference:
https://buildingrecommenders.wordpress.com/2015/11/10/the-components-of-a-recommender-system/