I'd say the only reason there is to avoid masturbation that makes it worth considering, if it can be proven conclusively, would be that partaking in the act results in suboptimal cognition compared to if one were to abstain from it. Even if that were true, it would only be a tiny minority of the human population, even of those who attempt to abstain, who ever cross the threshold from being sexually repressed to genuinely relinquishing their sexual desire. It is not worth feeling shame for what only the exceptional can accomplish in such case.
Most likely, this shame of masturbation typically stems from one's failure to maintain any fulfilling sexual or even platonic relationships, in which case it comes to be seen as a coping mechanism to put up with ideas that one has about themselves as being sexually undesirable, unskilled, or deviant. While you might say it's good that it deters you from seeking sexual relationships, chances are, what you really think is that it's good that it spares you from making the gamble with your own heart that comes from any intimate involvement with another person, because you fear that it is too fragile to withstand any turbulence that it entails even when you still desire the benefits, and so you make do with simulating the experience of those benefits without getting the full package. Unless you can disprove this to yourself, you have very little chance of consistently abstaining from masturbation, if any part of you truly considers that to be your purpose.
