This was the question which bothered me till I entered high school of a gurukul (ashrama). Usually when you see any famous old hindu temple you will find some pretty young girls who are wearing almost no clothes are carved on the temple. In fact temples in kajuraho & konark have become world famous bcoz of the same reason where you will find almost all the postures of kamasutra including postures of groupsex are on the temple. Any ordinary human being will think that this is disgusting to have such things on the temple which is the place of worship.
If sex is so dirty and vulgar then why should we all do it? Let us all stop having sex and soon the entire human race will be extinct. Sex is the source of creation of another living being and creation is the process of the creator the god. God is holy and he creates and does only holy things. God has created us and sex, which leads to creation and the continuity of life. Creation is a godly process (some have mistaken it with having multiple wives with many kids per wife) and it should not be seen as a taboo. Vaishnavism a sect of Sanathana dharma (Hinduism) advices against illicit sex i.e., sex for procreation only and not after that but shaivishm nothing is prohibited but it only states that the more you give up all the worldly pleasures the more you will be near to god. In fact the highest status(sahasradhara chakra) of kundalini yoga requires the sidhas/yogi to consume nothing other than the thin air and light.
Most of these statues are only on the exteriors of the temple and once you near the garbagraha (chamber of god) you will find no such statues. Imagine yourself in front of the garbagriha and all statues depicting the worldly pleasures such as sex are outside and on the wall of the temple. This suggests that to go near god you have to abstain from all these worldly and human pleasures like sex and devote yourself only to god with nothing in mind other than the deity himself. Unfortunately almost all of our today’s generation of parents do not know such simple things about their own dharma and they do not know how what to say when they are faced with such question by their children.