I don't think we should fault Jehovah's Witnesses for keeping strict moral codes regarding marriage and sex. They are not Watchtower rules. They are God's laws to keep his people clean and upright. Civilization itself rests upon the family. The bond between husband and wife is sacred. When it is broken, civilization itself suffers. Most religions in the world recognize the sanctity of marriage and the proper use of sex.
P.S. I saw an interesting TV program that dealt with the Puritans. The Puritans had anything put a "puritanical view" of sex. According to the show, even pre-marital sex was not forbidden provided the man married the maid when she became pregnant. Puritans viewed sex as a natural function...but one that had to be within the structure of the community and family. On the other hand, adultery was condemned since it broke the family and community ties.