The Old Testament is filled with warnings against idol worship and causing children to pass through the fire to moloch. Jesus came only to the lost sheep of Israel, lost because their religious leaders were leading them astray with false doctrines (same thing as today.) He tells an assembled crowd that it would be better for one that hurt this child to never have been born at all. It's not hidden, it was just more imperative for Him to save souls rather than to condemn them.