I remember going on a trip to a Cathedral as a child during primary school. Similarly, my primary school also offered trips to other religious buildings such as Hindu Temples. I found that the experience allowed me to better understand those of a different viewpoint as a child, which is becoming more important as we move into a more multicultural society here in Britain.
However, there's nothing wrong with parents refusing to allow their children to visit such places if they don't feel comfortable, though I feel that the reason these parents gave was a bit worrying. Despite this, forcing people to pay fines and go to court is more likely to lead to a more divisive society rather than a unifying one.