Because masturbation is unnatural... Masturbation (like homosexuality) ignores or bypasses that natural arrangement. It is one form of leaving 'the natural use of the female' for 'one contrary to nature'... Because the practice is one 'contrary to nature,' the masturbator pays a mental penalty. The habitual practice cripples his social and emotional development, hinders his attaining a healthful outlook and attitude toward the other sex and toward people in general. It can 'turn the person inward' upon himself, making him introverted. Or it can, and frequently does, lead into homosexuality, in which the person, not satisfied with his lonely sexual activity, seeks a partner for mutual sex play." (Watchtower, 1973 September 15, pages 564-565.)
who on earth wrote that shit ?