Even if the physical benefits to masturbation were substantial, which I doubt, they would not justify the negative results. Masturbation conflicts with the whole purpose of sexuality. The act of sexual intercourse is the physical expression of the marriage vows made at the altar. It is therefore an expression of Christian love, i.e., concern for the other. It is the most complete way of expressing the total self-donation of one person to another. Total means until death. It can’t be total for a week or a couple of years.
With masturbation there is no self-donation to anybody. It consists of taking pleasure for oneself alone. There is no giving at all. We were created for more than that.
The Church is not hostile to sex; indeed, nowhere will you find a higher understanding of sexuality than in the Catholic Church. The Church teaches reality. Opinions don’t change reality. Nor will the Church ever attempt to do so. I suggest that you get a copy of Good News About Sex and Marriage by Christopher West. You can order it through shop.catholic.com or by phone: 888 291 8000.