Actually the teaching & explanations are entirely logical, rational, and consistent with its own philosophical & moral premises, which are:
–that our bodies are gifts from God, not ours to possess, pervert, misdirect. (Also not to mutilate, neglect, etc.)
–that our bodies are temples of the Holy Spirit. (Read St. Paul)

–that sexuality is a gift, intended to be used in partnership with a committed person of the opposite gender in a marital bond.
–that orgasm in particular is a very sacred gift, meant only to be experienced in the unitive relationship of marriage. It is sacred not only because it is the culmination & apex of self-emptying (literally & figuratively), but because it also contains physically the elements of procreation to which God has granted us a share, as partners with him.
…and that masturbation is a violation of all the above 4 points.
^ That’s the short version, not the weightier version, but it’s sufficient & complete enough to satisfy “logical” and “reasonable.”