There are certain rules to be observed to enter into a premises. We should understand the difference between picnic and pilgrimage. Even Hindu scholars explain that temple worship is the entry level for further progress in spiritual development and ultimate salvation i.e. Moksham or Mukthi. The Devine Power is not visibly seen with out naked eyes. It is a faith. Hence why question if a punyaham is {purification act} is done to the temple premises. If we cannot see the impurities left in the premises by entry of a person, why bother for the act done by the temple priests in doing the purification. A temple is basically different from a Church or Mosque. Let us not try to club the three as Three in one. That can be practiced in our mind which is also a temple.
