If my SO jerks off. Seriously. I guess I would care if he chose that over me consistently, but if he chooses that over me once in a while, fine. Treat yo self. I do not think he has ever rejected me to masturbate.
Yesterday a close friend was complaining that she caught her boyfriend yanking it. I can see how that is a little embarassing, but she kept going on about how disgusting it is (I thought she was pretty sex positive). Really? Disgusting? To add to it, she put a moratorium on masturbation. Apparently, he should not want to if he is in a relationship.
Dude, masturbation is not a big deal. If they are struggling in the bedroom, I understand this reaction - but to act like it is inherently unacceptable is a pretty shitty way to stifle your partner. It is also extremely sex negative - it feels a bit Puritanical.
Sorry if I have rubbed anyone wrong; I just think that in or out of a relationship, you should have the privilege of treating yourself to this pleasure.