It takes a special kind of justifier to claim masturbation is better than sex, let alone equal to one another, assuming nothing's wrong with their ability to perform or something.
Even for people who have no interest in who the hole is they're plunging into, they will take that over masturbating unless there is something in their minds blocking them off from the choice. They will go to a bathroom stall and stick it through a hole drilled into it rather than just opt for another night of internet porn, as there is far more going on here. There's smells, sounds, and the physical sensation has a way of putting the brain into some other place. Even something as simple as feeling a sense of movement that is not your own does things.
More likely it's that sexual turn-on lowers inhibitions, which is why you can see people who 'would never do that' giving into things that surprise them after the fact. With a narcissist you'd then see their need for control come out as their brand of sex, assuming that's the direction the sex-addicted narcissist even took (there are narc subs).
Ę̵̚x̸͎̾i̴͚̽s̵̻͐t̷͐ͅe̷̯͠n̴̤̚t̵̻̅i̵͉̿a̴̮͊l̵͍̂ ̴̹̕D̵̤̀e̸͓͂t̵̢͂e̴͕̓c̸̗̄t̴̗̿ï̶̪v̷̲̍é̵͔
