Basically you can selectively "patch" ebooks to censor profanity, sex scenes, violence, (and more) depending on your tastes and on what you like (and don't like) to consume.
However, this is extremely unpopular with authors/publishers for the same reason that censoring movies is extremely unpopular with Hollywood (hence why companies like VidAngel are constantly mired in legal issues despite widespread popularity with consumers).
Honestly, I don't understand why since at the end of the day everyone gets paid, and indeed get paid more than they normally would have (I guess it's more of a "you are altering my art so people can consume it in ways I didn't intend" attitude). But in my mind it's no different from using whiteout on a physical book or picking out the mushrooms (or whatever you don't like) in some chef's dish.
Basically, I've already built the tech to do this for myself privately (and have patch files for ASoIaF and a dozen other epubs), but I will never share it (I've even considered FOSS) except with close family and friends even though I know it would be wildly popular in places like Utah because I fear legal pursuit from authors/publishers (and since you must break DRM in order for the tech to work, I don't see a way out).