I am from Cochin and I heard that all christians were allowed to enter in temple in the past. This practice ceased once they assembled for "Udayamperur Sunnahadose" (This place is 12 km fm Cochin)- a high level christian meeting centuries ago, and declared themselves as non-believers in the rituals followed (I will not use Hindu rituals as I believe Hinduism is a way of life and not a religion) in the state of Cochin. Even in Kerala all children born are without religion unless they are inducted into one - and one question remains, how can a member of Christian/ Muslim religion follw idol worship? then they cease to be a christian or muslim!!
