I know many christian parents feel their children need to be protected from the influence of others, too.
I have never felt that way myself. I never felt that I should be the main arbiter in all things. Yes, it was important to me that my children understand right and wrong, that essentially they have consciences, that they care about others. Otherwise I wanted them to learn to think for themselves more than anything else. I have strong feelings and beliefs about some things and I am sure those beliefs came across in our everyday lives. We often hear that it is better to "model" your belief than just to talk about it. Saying "don't smoke" and then drawing on a cigarette isn't a good way to teach children.
I know I am considered wimpy because of my willingness to let my children explore. I don't know to this day if it was the right path to follow. I suspect I could have been a better guide. But I don't think I was wrong to allow my children to hear others' voices. I could have provided a better, more cushioned space for them in their explorations - I don't think I did that - but fundamentally I do not believe in shielding children from the beliefs of others.