What Can Phillips Mean?

Adam Phillips somewhere calls masturbation 'not only safe sex, it's safe incest.' I wonder about this: really? Is there any kind of traction in this? My first sense is that there's not; because the main point of similarity between the two sex acts (putting aside the jejune notion that since you are a part of your family, having sex with yourself is equivalent to having sex with somebody in your own family) -- broadly, that it's a sex act of convenience, a close-to-hand opportunistic sex act -- is massively outweighed by the main difference: masturbation is victim free, where the overwhelming number of instances of incest are also instances of abuse. What can Phillips mean?