I do not think it would take an Einstein to see some relationship between masturbation and selfishness (which here i decide to call self-centredness). There must not be scientific proof to make everything true. If it were so, scientists could have given us an answer concerning the hard problem of consciousness. How is it that the physical phenomenon of the aroma from a cake is able to create some effect on the consciousness of the perciever of cake and not another thing? That it is yet to be explained is does not mean that there is no connection becasue each person is aware of the aroma. I do not want to go into the problem attempted an answer by Chalmers et al. Still there is a relationship between masturbation and self-centredness. (I have decided not to look into whether it is appropriate to be selfcentred and why so ornot).
Human sexuality from all intent was geared towards a union between two subjects. Going by the most basic evidence which is the conjugal organs, one is meant to enter the other. Sexual drive in organisms (man inclusive) apart from bringing about some ectstasy or at least some satisfaction, moves towards perpetuity of the species involved. The satisfaction would seem to be eventual to the main design for sex. Today, the opposite is the case.
It is not difficult to see that when the sexual act is not directed towards another, it is going pervert, to say the least, becomes self...