To respond to OP, 50 shades and stuff like that are books and while they dont contain graphical content they can still arouse some ladies. They are "socially" acceptable.
You will judge but you wont say anything to someone reading 50 shades in the library.
However if someone wouldve been watching porn beside me on an airplane, i wouldve kindly asked him to either shut it off as some kids might be around, or to go whack it once we land.
If he had some sounds playing, wouldnt "public disturbance" apply in this case?