One thing to keep in mind is that during a flight what appears on your computer screen displayed as text my not be clearly visible from the isle.
But human figures on screen can be seen from a greater distance and could be observed from the isle. So this may be a situation that not only affects the person sitting next to the one who decides to watch unsavory video's but it could also affect children or others on a flight who either desides to walk the isle's for exercise or need to use the facilities.

It's human nature to look at what people are during during a flight even it it's no more than a glance. That especially is true when it comes to computer screens. With this in mind IMHO a person who subjects others to visual images that are in very very bad taste should be asked to respect the rights of others not to be subjected to what most of society regard as filth.

But just a question. How is this any different than two naked people getting it on in the seat right next to you? Would that be acceptable?

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"What you hear in a great jazz band is the sound of democracy. “The jazz band works best when participation is shaped by intelligent communication.”
Harmony happens whenever different parts get to form a whole by means of congruity, concord, symetry, consistency, conformity, correspondence, agreement, accord, unity, consonance…….